plan: prep.1 type-scoped namespacing — 5-task atomic resolver + 12-fixture migration (refs #31)

The plan covers the first iteration of the kernel-extension-mechanics
milestone: type-scoped `<TypeName>.<member>` resolution in
`ailang-check`, narrowed `BareCrossModuleTypeRef` /
`BadCrossModuleTypeRef` diagnostics in `ailang-core::workspace`,
two new `CheckError` variants, CLI diagnostic-message rewording,
and atomic rewrite of 12 `.ail` example fixtures from `std_X.Y` to
the type-scoped form. Five tasks, each unit-of-review.

Includes a spec correction (same commit because plan recon
surfaced it): the prep.1 Blast Radius previously claimed
`hash_pin.rs` + `prelude_module_hash_pin.rs` refreshes and a
`design_schema_drift.rs` pin addition. Plan-recon walked every
test crate (per the schema-camelcase-fix hash-pin-blast-radius
lesson) and found:
  * neither hash-pin file pins any fixture in prep.1's migration
    set — refresh is empty;
  * type-scoped resolution is a checker-only change (no new JSON
    tags, no AST shape change) — the drift pin belongs to prep.2
    (`Term::New`) and prep.3 (`kernel: true` + `param-in`), not
    prep.1.

Spec section 'Blast radius' and the 'Iteration scope' summary now
reflect the recon-cleared reality.

docs/specs/0052-kernel-extension-mechanics.md

@@ -139,36 +139,52 @@ collision disambiguator (no current collisions exist).
 
 **Blast radius.** Per `grep -rE 'std_(maybe|pair|list|either)\.' examples/ crates/`:
 
-- **`.ail` example fixtures** (~14 files): `ct_2_bare_cross_module.ail`,
+- **`.ail` example fixtures** (12 with cross-module refs, plus the
+  three defining modules with no refs): `ct_2_bare_cross_module.ail`,
   `ct_3b_bad_qualified_known_module.ail`, `nested_pat.ail`,
-  `std_either.ail`, `std_either_demo.ail`, `std_either_list.ail`,
+  `std_either_demo.ail`, `std_either_list.ail`,
   `std_either_list_demo.ail`, `std_list.ail`, `std_list_demo.ail`,
-  `std_list_more_demo.ail`, `std_list_stress.ail`, `std_maybe.ail`,
-  `std_maybe_demo.ail`, `std_pair.ail`, `std_pair_demo.ail`.
-  Each rewritten from `std_X.Y` to `Y` (type-scoped) where Y is
-  type-associated. The defining modules (`std_maybe.ail` etc.)
-  may keep their internal references unchanged (intra-module refs
-  are bare today already).
-- **Corresponding `.ail.json` fixtures** for round-trip and hash-pin tests.
-- **Hash-pin files** (2): `crates/ailang-core/tests/hash_pin.rs` and
-  `crates/ailang-surface/tests/prelude_module_hash_pin.rs`. Both
-  refreshed with new hashes. Each refresh carries an Honesty-Rule
-  provenance comment quoting the prep.1 commit and naming the
-  surface change.
+  `std_list_more_demo.ail`, `std_list_stress.ail`,
+  `std_maybe_demo.ail`, `std_pair_demo.ail`. Each rewritten from
+  `std_X.Y` to `Y` (type-scoped) where Y is type-associated. The
+  three defining modules `std_either.ail`, `std_maybe.ail`,
+  `std_pair.ail` contain no cross-module references and need no
+  body changes (intra-module refs are bare today already).
+  `ct_2_bare_cross_module.ail`'s role flips semantically: it stays
+  RED (the unimported bare type case still fires
+  `BareCrossModuleTypeRef` under the narrowed rule), but the
+  diagnostic *message* it asserts is the new one.
+- **No corresponding `.ail.json` fixtures.** None of the 15
+  spec-named `.ail` files have a sibling `.ail.json` round-trip
+  pin in the tree.
 - **Source-side reference** in `crates/ailang-{check,codegen,surface}/src/`
-  and `crates/ail/tests/e2e.rs` (~7 files): inspect during recon
-  whether they hardcode `std_maybe`/`std_pair`-style identifiers
-  in diagnostic strings or test fixtures. Diagnostic strings
-  update to new vocabulary; test fixtures update to type-scoped.
-  Production type-resolution logic is the new code.
-- **Drift test** `crates/ailang-core/tests/design_schema_drift.rs`
-  gains a new pin that exercises the type-scoped resolution end-
-  to-end at the schema level.
+  and `crates/ail/tests/e2e.rs` (7 files): doc-comments and
+  test-helper code mentioning `std_X.Y` vocabulary update to
+  type-scoped vocabulary. Production type-resolution logic is the
+  new code. The specific sites are enumerated in the prep.1 plan.
+- **CLI diagnostic renderer + assertion update**:
+  `crates/ail/src/main.rs:1249-1278` (the `BareCrossModuleTypeRef`
+  and `BadCrossModuleTypeRef` translation arms) and
+  `crates/ail/tests/ct1_check_cli.rs:154` (an assertion on the old
+  "ail migrate-canonical-types" hint string) move with the
+  diagnostic-message narrowing.
 
-The 14 `.ail` examples are rewritten atomically with the resolver
-change in a single iteration commit. Walking *every* test crate
-for hash-pin sites is mandatory (per the
-`hash-pin blast-radius audit` lesson from `schema-camelcase-fix`).
+**No hash-pin or schema-drift work in prep.1.** The hash-pin audit
+across every test crate (per the `hash-pin blast-radius audit`
+lesson from `schema-camelcase-fix`) is mandatory and was performed
+during prep.1's plan recon. Result: `crates/ailang-core/tests/hash_pin.rs`
+pins `sum.ail`, `list.ail`, `ordering_match.ail`,
+`test_22b1_dup_a.ail`, `test_22b1_dup_classmod.ail` — none of which
+contain `std_X.Y` references; `crates/ailang-surface/tests/prelude_module_hash_pin.rs`
+pins `prelude.ail` — also no `std_X.Y` references. **No pin refresh
+applies to prep.1.** The `prelude_module_hash_pin.rs` refresh
+happens in prep.3 when `kernel: true` lands on the prelude module.
+Schema-drift pins in `crates/ailang-core/tests/design_schema_drift.rs`
+also do not apply: type-scoped resolution is a checker change with
+no new JSON tags, no new enum variants, no AST shape changes. The
+drift pins for this milestone land in prep.2 (new `t: "new"` tag,
+new `NewArg` JSON) and prep.3 (new `kernel`, `param-in` schema
+attrs).
 
 **Integration with existing mechanisms.**
 
@@ -702,8 +718,10 @@ Milestone closes when:
 The plan that follows this spec carves the work into three
 iterations:
 
-- **prep.1** — Type-scoped namespacing. Resolver change + 14
-  example rewrites + 2 hash-pin refreshes.
+- **prep.1** — Type-scoped namespacing. Resolver change + 12
+  example rewrites + diagnostic-message narrowing + ct1_check_cli
+  assertion update. No hash-pin or drift-test work (audit cleared
+  during plan recon; pins live in prep.2/3).
 - **prep.2** — `Term::New`. AST + surface + checker arg-kind
   enforcement.
 - **prep.3** — Kernel-tier modules + `param-in`. Schema +