iter prep.1-type-scoped-namespacing (DONE 5/5): TypeDef-first resolution + workspace pre-pass — closes #31

First iteration of the kernel-extension-mechanics milestone. Ships
the type-scoped `<TypeName>.<member>` resolution path as the
canonical form for type-associated operations, narrows the
`BareCrossModuleTypeRef` / `BadCrossModuleTypeRef` diagnostics from
"bare = strictly local" to "bare = in-scope by any path", migrates
12 std-library example fixtures, and introduces a workspace-wide
normalisation pre-pass `prepare_workspace_for_check` shared between
`check_workspace` and `monomorphise_workspace`.

Architectural discovery during implementation: the plan covered the
`Term::Var` dot-qualified resolver layer plus the workspace
validator's bare-name acceptance, but the migration of bare-form
fixtures exposed five sites where bare vs. qualified type-names
needed symmetric treatment — `Term::Ctor` resolution, `Type::Con`
well-formedness, mono's poly-free-fn name/constraint-count
enumeration, codegen's `lookup_ctor_by_type` bare-name path, and
the upstream desugar-then-qualify composition. Rather than
scattering TypeDef-first ladders across each site, the implementer
centralised the work into one pre-pass that walks every consumer
module's `Type::Con.name` and `Term::Ctor.type_name`, rewriting
bare cross-module references to their qualified `<home>.<Type>`
form. This is symmetric to the pre-existing `qualify_local_types`
(owner-side); the new pre-pass is the consumer-side mirror.
Downstream passes see qualified Types regardless of authoring form.
The TypeDef-first ladder still lives in `synth`'s `Term::Var` arm
because `<TypeName>.<member>` is term-position-only — `Maybe.from_maybe`
is a Var, not a Type expression, and the pre-pass does not rewrite
Var names.

Alternatives considered:

(a) Add TypeDef-first ladder at every resolution site separately
    (the plan's implicit assumption). Rejected: O(N) extension
    sites, each carrying the same workspace-walking logic; the
    pre-pass version is O(1) — one pass, every downstream consumer
    benefits.
(b) BLOCKED + spec re-brainstorm. Rejected: the architecture
    extension is consistent with prep.1's thesis (bare type-name
    resolves to the workspace-wide TypeDef) and forward-compatible
    with prep.2 (Term::New.type_name falls under the same rewrite)
    and prep.3 (kernel-tier TypeDefs enter the workspace map
    automatically). No design regression to bounce back over.

Spec updated to document the realisation mechanism honestly: the
"Realisation mechanism — workspace pre-pass" subsection clarifies
that the resolver-level semantics described in "Implementation
shape" are the user-facing contract, and the actual code path is
the pre-pass.

Verification:

- `cargo test --workspace`: ALL GREEN. 87 e2e + every crate's unit
  + integration tests pass with no regressions.
- Three NEW in-source tests pin Task 1's resolver paths:
  `type_scoped_member_resolves`, `type_scoped_member_not_found`,
  `type_scoped_receiver_not_a_type`.
- One NEW workspace test pins the narrowed validator:
  `ct1_validator_accepts_bare_with_explicit_import`.
- One renamed-and-flipped existing test:
  `ct1_validator_rejects_bare_xmod_with_import_candidate` →
  `ct1_validator_accepts_bare_xmod_with_import_candidate` (the
  bare-with-import path is now ACCEPTED).
- One NEW companion test for the workspace-wide ctor lookup:
  `ct2_term_ctor_bare_cross_module_via_workspace_resolves`.
- Two pre-existing tests' assertions updated for the new error
  wording: `ct1_check_cli::check_human_mode_emits_actionable_message_to_stderr`
  and `crates/ailang-check/tests/workspace.rs::unknown_module_prefix_is_reported`.
- 12 migrated `.ail` fixtures verified via the existing e2e
  suite (each fixture is the test runner's target for an existing
  `build_and_run` assertion).
- Negative fixture `ct_2_bare_cross_module.ail` semantically
  preserved: dropped its `(import std_maybe)` so bare `Maybe` is
  out-of-scope under the narrowed rule and still fires
  `BareCrossModuleTypeRef`.

Concerns:

- The pre-pass introduces a new architectural layer (consumer-side
  qualification) that the spec did not originally anticipate. Spec
  amendment in this commit documents the layer. Future iterations
  reference `prepare_workspace_for_check` as established
  infrastructure.
- `examples/test_ct1_bare_xmod_rejected.ail.json` switched its
  offending name from bare `Ordering` (which under the prep.1
  semantics may now resolve via implicit prelude) to a still-
  unresolvable `Mystery_Type`. The CLI test's intent (assert that
  a human-mode `ail check` exits non-zero on a still-RED case) is
  preserved.

Milestone status: kernel-extension-mechanics (Gitea #6) advances
1/3 iters. Next: prep.2 (`Term::New` construct) issue #32.

crates/ail/tests/e2e.rs

@@ -361,13 +361,12 @@ fn parameterised_maybe_match() {
 
 /// cross-module reference to a parameterised ADT, including
 /// its ctors and a polymorphic combinator instantiated at `(Int, Int)`.
-/// `std_maybe_demo` imports `std_maybe`, qualifies the type-name slot
-/// of every `term-ctor` (`std_maybe.Maybe`), and exercises
-/// `from_maybe`, `is_some`, `is_none`, and `map_maybe` once each.
-/// Property protected: the qualified-only convention (the
-/// authoring surface's architectural pin extended to types and
-/// ctors per the brief)
-/// flows end-to-end through check, codegen, and runtime.
+/// `std_maybe_demo` imports `std_maybe` and (prep.1 migration) uses
+/// the type-scoped form: bare `Maybe` at every `term-ctor` type-name
+/// slot, `Maybe.from_maybe` / `Maybe.is_some` etc. for the
+/// combinators. Exercises four combinators once each. Property
+/// protected: prep.1's type-scoped namespacing flows end-to-end
+/// through check, codegen, and runtime.
 #[test]
 fn cross_module_maybe_demo() {
     let stdout = build_and_run("std_maybe_demo.ail");
@@ -376,12 +375,13 @@ fn cross_module_maybe_demo() {
 }
 
 /// drives the polymorphic `std_list` combinators end-to-end.
-/// Exercises a recursive cross-module ADT (`std_list.List<a>`) consumed
-/// from a separate module that also imports `std_maybe`. Guards the
-/// `qualify_local_types` propagation in both `Term::Ctor` synth and
-/// `Term::Match` field binding — without it, recursive ctor fields
-/// (`Cons a (List a)`) stay unqualified at the cross-module use site
-/// and fail to unify against the qualified scrutinee args.
+/// Exercises a recursive cross-module ADT (`List<a>` from `std_list`,
+/// prep.1 type-scoped form) consumed from a separate module that
+/// also imports `std_maybe`. Guards the `qualify_local_types` /
+/// `qualify_workspace_types` propagation in both `Term::Ctor` synth
+/// and `Term::Match` field binding — without it, recursive ctor
+/// fields (`Cons a (List a)`) stay unqualified at the cross-module
+/// use site and fail to unify against the qualified scrutinee args.
 #[test]
 fn std_list_demo() {
     let stdout = build_and_run("std_list_demo.ail");