spec: 23 — correct prep-commit reachability against main

Brainstorm assumed all four 23.4-prep commits had shipped to main.
Branch verification (post-iter/23.4 deletion) showed only prep1
(linearity + check bare-name) is on main; prep2 + prep3 were
attempted on the stranded iter/23.4 branch and never landed.

Spec corrections:
- Goal section: prep-commit status block reflects actual main state.
- Architecture: drop §2 (prep2/prep3 rollback) — no rollback exists
  on main; section count drops from four to three artefacts.
- Components table: prep2/prep3 row now reads 'abandoned 2026-05-11
  with iter/23.4 deletion', not 'shipped, rolled back in 23.4'.
- Acceptance criterion 1: drop the 'prep2 + prep3 are rolled back'
  clause.
- Load-bearing assumption 5: now states prep2/prep3 never reached
  main (fixes the silent-assumption pattern this spec exists to
  prevent — same failure mode the original Spec-23 had).
- Load-bearing assumption 6: cite the cherry-picked main SHAs
  (0caaced, 923dd8c) alongside the stranded-branch originals
  (8d39f13, aef4ab8).
- Known costs: drop the '23.4 rollback' line item.

docs/specs/2026-05-11-23-eq-ord-prelude.md

@@ -32,10 +32,20 @@ seam.
 
 The corrected architecture unifies the two specialisers (see
 Architecture below) and ships the remaining free fns on top of
-the unified pass. The three iter-23.4 prep commits are classified:
+the unified pass.
-prep1 (linearity + checker bare-name) stays load-bearing, prep2 +
+
-prep3 (codegen bare-name fall-throughs) become provably dead and
+**Prep-commit status (verified against main 2026-05-11 after
-are rolled back in 23.4.
+iter/23.4 branch teardown):** prep1 (linearity + checker
+bare-name) landed on main on 2026-05-11 via cherry-pick from the
+stranded iter/23.4 branch; it stays load-bearing. prep2 and prep3
+(codegen bare-name fall-throughs) were attempted on the stranded
+iter/23.4 branch and *never reached main*; with iter/23.4 deleted,
+they are abandoned as git history without a rollback step. Their
+architectural intent — make codegen handle bare polymorphic
+free-fn names directly — is superseded by the mono-unification.
+The unified pass rewrites bare polymorphic call sites to mono
+symbols before codegen runs, making the fall-throughs structurally
+unnecessary.
 
 `Show`, operator routing, `print`-rewire, and the heap-Str ABI
 remain out of scope; each is its own milestone with substantive
@@ -44,7 +54,7 @@ reasons (see "Out of scope" — unchanged from original spec).
 ## Architecture
 
 The milestone no longer consumes the 22b.3 typeclass machinery
-unchanged. Four artefacts:
+unchanged. Three artefacts:
 
 ### 1. Mono-Pass unification (the corrected centrepiece)
 
@@ -80,33 +90,7 @@ sites of `lower_polymorphic_call` (lines 1944, 1972) become direct
 calls to mono symbols after the typecheck-mono walker has rewritten
 them.
 
-### 2. Rollback of iter-23.4-prep2 + prep3
+### 2. Prelude AILang module
-
-Two existing codegen bare-name fall-throughs were anticipatory
-patches for the prelude free fns:
-
-- commit `a06159d` (prep2): codegen — bare-name fall-through to
-  implicit-imported free fns.
-- commit `c42a0f5` (prep3): codegen — polymorphic-free-fn bare-name
-  fall-through to implicit-imported modules.
-
-After Mono unification, codegen never sees bare polymorphic free-fn
-names — the unified mono pass rewrites every call site to its mono
-symbol before codegen runs. The two patches are provably dead and
-are rolled back in 23.4. The rollback lands in the same iter as
-the unification so the codebase never carries the fall-throughs
-as visible-but-dead code.
-
-The third iter-23.4-prep is kept:
-
-- commit `8d39f13` (prep.1): linearity — register `Def::Class` method
-  types in globals. Required independent of mono — linearity walks
-  pre-mono.
-- commit `aef4ab8` (prep.2): check — bare-name fall-through to
-  implicit-imported free fns. Required at typecheck time — bare `ne`
-  must resolve to the prelude `Def::Fn` *before* mono can specialise.
-
-### 3. Prelude AILang module
 
 `examples/prelude.ail.json` already contains, from iters 23.1–23.3:
 the `Ordering` ADT, the `Eq` class with `Eq Int`/`Bool`/`Str`
@@ -119,7 +103,7 @@ Iter 23.5 adds the five free fns:
   bodies pattern-matching `compare` against the appropriate
   `Ordering` shapes.
 
-### 4. C-runtime functions
+### 3. C-runtime functions
 
 `runtime/str.c` shipped its two functions in iter 23.2 and 23.3:
 `ail_str_eq(a, b) -> bool` (byte-equality on constant-string layouts)
@@ -139,9 +123,9 @@ Int/Bool/Str is acknowledged and ratified as transitional.
 | 23.1 | shipped (2026-05-10) | `Ordering` ADT + prelude skeleton + auto-load via `check_workspace`. |
 | 23.2 | shipped (2026-05-10) | `class Eq` + `Eq Int/Bool/Str` + `ail_str_eq`. |
 | 23.3 | shipped (2026-05-10) | `class Ord extends Eq` + `Ord Int/Bool/Str` + `ail_str_compare`. |
-| 23.4-prep | shipped, **kept** | commits `8d39f13` (linearity registers `Def::Class` method types in globals) + `aef4ab8` (check bare-name fall-through to implicit-imported free fns). Both resolve names *before* mono; independent of B1. |
+| 23.4-prep | shipped to main 2026-05-11 (cherry-picked from stranded iter/23.4), **kept** | commits on main: `0caaced` (linearity registers `Def::Class` method types in globals) + `923dd8c` (check bare-name fall-through to implicit-imported free fns). Both resolve names *before* mono; independent of B1. |
-| 23.4-prep2 / 23.4-prep3 | shipped, **rolled back in 23.4** | commits `a06159d` + `c42a0f5` — codegen bare-name fall-throughs. Provably dead after Mono unification. |
+| 23.4-prep2 / 23.4-prep3 | **abandoned 2026-05-11 with iter/23.4 deletion** — never reached main | Attempted-but-stranded commits were `a06159d` + `c42a0f5` (codegen bare-name fall-throughs); they were anticipatory patches for an approach (codegen-time bare-name handling) the mono-unification supersedes. No rollback step is needed because no rollback target exists on main. |
-| **23.4** (revised) | upcoming | **Mono-Pass unification.** Restructure `crates/ailang-check/src/mono.rs::monomorphise_workspace` into one specialiser with two source-body entry points (class-method via `Registry::entries`, free-fn direct). Extend `collect_mono_targets` to also produce targets for polymorphic free-fn calls with fully-concrete substitutions. Remove `lower_polymorphic_call` + `module_polymorphic_fns` + `mono_queue` from codegen. Rollback prep2 + prep3. Amend DESIGN.md §"Resolution and monomorphisation" to describe the pass as covering all `Type::Forall`-Defs. Tests: existing polymorphic fixtures (`poly_id`, `poly_apply`, `poly_rec_capture`) green; new fixture `cmp_max_smoke` proves cross-cutting (`cmp_max : forall a. Ord a => (a, a) -> a` at Int synthesises both `cmp_max__Int` and nested `compare__Int` in one fixpoint). |
+| **23.4** (revised) | upcoming | **Mono-Pass unification.** Restructure `crates/ailang-check/src/mono.rs::monomorphise_workspace` into one specialiser with two source-body entry points (class-method via `Registry::entries`, free-fn direct). Extend `collect_mono_targets` to also produce targets for polymorphic free-fn calls with fully-concrete substitutions. Remove `lower_polymorphic_call` + `module_polymorphic_fns` + `mono_queue` from codegen. Amend DESIGN.md §"Resolution and monomorphisation" to describe the pass as covering all `Type::Forall`-Defs. Tests: existing polymorphic fixtures (`poly_id`, `poly_apply`, `poly_rec_capture`) green; new fixture `cmp_max_smoke` proves cross-cutting (`cmp_max : forall a. Ord a => (a, a) -> a` at Int synthesises both `cmp_max__Int` and nested `compare__Int` in one fixpoint). |
 | **23.5** (revised) | upcoming | **Prelude free fns + E2E.** Add `ne`/`lt`/`le`/`gt`/`ge` to `examples/prelude.ail.json`. E2E fixtures: (a) positive polymorphic helper at Int/Bool/Str, (b) negative — `eq f g` at Float typecheck-rejects with Float-aware diagnostic, (c) user-ADT — `IntBox` with `Eq`/`Ord` instances + polymorphic helper monomorphises to the user instance. Amend DESIGN.md §"Decision 11 / Prelude classes" — Eq/Ord shipped; the "Milestone 22 ships no built-in Prelude classes" wording stays as historical accuracy with a forward-pointing addendum. Roadmap: P1 Post-22 Prelude entry from `[~]` to `[x]` for Eq/Ord half; Show half stays. |
 
 ## Data flow
@@ -271,8 +255,8 @@ The milestone closes when:
 1. **23.4 has landed:** `crates/ailang-check/src/mono.rs::monomorphise_workspace`
    synthesises both class-method and polymorphic-free-fn mono Defs
    in one fixpoint loop. `crates/ailang-codegen/src/lib.rs::lower_polymorphic_call` +
-   `module_polymorphic_fns` + `mono_queue` are removed. Commits
+   `module_polymorphic_fns` + `mono_queue` are removed. (prep2 +
-   `a06159d` (prep2) + `c42a0f5` (prep3) are rolled back.
+   prep3 were never on main; no rollback step in scope.)
 2. **DESIGN.md §"Resolution and monomorphisation" amended:** the
    pass description covers all `Type::Forall`-quantified Defs, not
    only class methods.
@@ -362,8 +346,6 @@ New under B1 unification:
   `crates/ailang-codegen/src/lib.rs` (`lower_polymorphic_call`,
   `module_polymorphic_fns` fields, `mono_queue` machinery). Net
   code reduction expected.
-- **23.4 rollback:** `git revert a06159d c42a0f5` plus adaptation
-  to the newly-dead code paths in codegen, estimated −80 LOC.
 - **23.5 prelude additions:** `examples/prelude.ail.json` +30-40
   lines (five free fns with Forall-constraint signatures and
   bodies). Three new E2E `.ail.json` fixtures, ~60 lines JSON.
@@ -394,14 +376,19 @@ relies on as currently-true.
    corresponding workspace Defs.
 4. `examples/prelude.ail.json` today contains no free fns (only
    ADT, classes, instances).
-5. Commits `a06159d` (prep2) and `c42a0f5` (prep3) added codegen
+5. prep2 and prep3 (the codegen bare-name fall-through patches)
-   bare-name fall-throughs that were anticipatory patches for the
+   *never reached main*. They lived on the stranded iter/23.4
-   prelude free fns; they have no currently-active load-bearing
+   branch which was deleted on 2026-05-11. The current main
-   case outside the still-not-shipped 23.4 free fns.
+   contains no codegen bare-name fall-through for polymorphic
-6. Commit `8d39f13` (prep.1, linearity) and commit `aef4ab8`
+   free-fn calls — codegen rejects bare polymorphic free-fn calls
-   (prep.2, check bare-name) operate at typecheck / linearity time
+   today, which is exactly what makes the original iter-23.4 BLOCK.
-   — before any mono pass — and are load-bearing for any prelude
+6. Commits on main `0caaced` (prep.1, linearity registers `Def::Class`
-   free-fn resolution regardless of mono architecture.
+   method types in globals) and `923dd8c` (prep.2, check bare-name
+   fall-through to implicit-imported free fns) operate at
+   typecheck / linearity time — before any mono pass — and are
+   load-bearing for any prelude free-fn resolution regardless of
+   mono architecture. (Originals from stranded branch: `8d39f13`
+   and `aef4ab8`; cherry-picked onto main 2026-05-11.)
 7. `crates/ailang-codegen/src/lib.rs::lower_polymorphic_call` is
    invoked from two call sites today (lines 1944, 1972), both of
    which become direct mono-symbol calls after 23.4.