iter raw-buf.6 kernel-stub-retirement (DONE 5/5): retire the stub, raw_buf is the sole base extension (refs #7)

Closes the raw-buf milestone. raw_buf (shipped raw-buf.1-.5; the
owned-drop resolution landed under bug #42/#43) has subsumed every
ratification role kernel_stub held -- Term::New end-to-end, the
param-in reject, kernel-tier auto-import, the monomorphic intrinsic
path, and the type-scoped polymorphic intrinsic mechanism (RawBuf's
four ops). The stub is now redundant; this iteration removes it.

Pure removal (-636/+49 across 22 files, 7 deleted):
- Rust surface: drop `mod kernel_stub` + `STUB_AIL` re-export
  (ailang-kernel), `parse_kernel_stub` + its workspace injection
  (ailang-surface), the `answer` + two `StubT_peek__{Int,Float}`
  INTERCEPTS entries + their three emit fns (ailang-codegen). The
  (intrinsic) markers leave with the deleted source, so the
  marker<->entry bijection holds in lockstep.
- Source + tests: delete crates/ailang-kernel/src/kernel_stub/,
  kernel_stub_module_round_trips, the two stub-consumer e2e tests,
  and mono_scoped_symbol.rs (its scope-qualified-mono mechanism is
  now pinned by RawBuf's ops + the intercepts bijection).
- Fixtures: delete kernel_answer.ail, new_stubt_smoke.ail,
  peek_mono_pin_smoke.ail, and fieldtest kem_3_stub_consumer.ail
  (referenced the deleted StubT; documented a since-fixed bug).
- Pins: re-baseline both workspace-count content-pins 5 -> 4
  (workspace_pin.rs + the e2e.rs twin) and regenerate all five IR
  snapshots (400 stub-IR lines removed; no user IR changed -- the
  stub auto-injected into every build).
- Ledger: design/INDEX.md + design/models/0007 to present-state
  (raw_buf is the live ratifier; raw-buf milestone shipped, series
  pending), plus architecture-comment sweep across workspace.rs,
  mono.rs, check/codegen lib.rs, workspace_kernel.rs.

Scope decisions (orchestrator, pre-plan): the self-contained inline
serde_json check-layer fixtures in ailang-check/src/lib.rs keep their
incidental StubT/kernel_stub sample names (they construct what they
reference; not stub-ratification) -- the one permitted residual.
kem_4 fieldtest kept (uses a user NumBox ADT, comment-only edit).
hash.rs `name: "answer"` left (generic serde doc example).

Plan-gap caught at implement: the planner's verbatim edit list
under-enumerated four honesty sites; one (mono.rs:562) carried a
literal `StubT_peek__Int` -- a hard-gate symbol the verbatim list
missed, which would have failed Task 4's removal gate. Filled
(comment-only, no behaviour). Confirms the planner self-review
filter-completeness risk; the implement gate caught it.

Verification: full workspace suite green (0 failed); hard symbol gate
(STUB_AIL|parse_kernel_stub|emit_answer|emit_stubt_peek|StubT_peek__)
zero matches across crates/ examples/ design/; soft gate residual only
the kept inline fixtures; kernel crate is lib.rs + raw_buf/ only.
Regression: compile_check 24/24 stable (exit 0; uniform downward
check_ms within tol -- stub no longer parsed per compile), cross_lang
25/25, check 34/34 stable (exit 0; an earlier exit-1 on
rc_over_bump was machine-load ratio noise -- denominator bump_s got
faster, rc_s also improved -- confirmed green on re-run, not
baselined).

design/INDEX.md

@@ -109,4 +109,4 @@ is the default.
 | authoring-surface | onboarding / evolves | design/models/0001-authoring-surface.md |
 | prose-projection  | onboarding / evolves | design/models/0006-prose-projection.md |
 | pipeline          | onboarding / evolves | design/models/0003-pipeline.md |
-| kernel-extensions | onboarding / evolves (mechanisms milestone closed 2026-05-28; ratified end-to-end by the `ailang-kernel/src/kernel_stub` fixture, planned for retirement when raw-buf lands a real second consumer; raw-buf and series milestones pending) | design/models/0007-kernel-extensions.md |
+| kernel-extensions | onboarding / evolves (mechanisms milestone closed 2026-05-28; ratified end-to-end by the `ailang-kernel/src/raw_buf` base extension; series milestone pending) | design/models/0007-kernel-extensions.md |

design/models/0007-kernel-extensions.md

@@ -4,9 +4,10 @@
 (`kernel-extension-mechanics`; iterations prep.1, prep.2, prep.3
 landed). The four language-level mechanisms — type-scoped
 namespacing, `Term::New`, kernel-tier modules + auto-import, and
-`param-in` — are shipped and ratified by the stub kernel module
-(`crates/ailang-kernel/src/kernel_stub/`). The base-extension and library-
-extension milestones (`raw-buf`, `series`) are pending. This
+`param-in` — are shipped and ratified by the `raw_buf` base
+extension (`crates/ailang-kernel/src/raw_buf/`). The base-extension
+milestone (`raw-buf`) has shipped; the library-extension milestone
+(`series`) is pending. This
 whitepaper describes the design as a coherent whole; the
 per-milestone specs in `docs/specs/` carry the implementation-
 level detail. Sections describing the now-shipped mechanisms read
@@ -220,7 +221,7 @@ generalised from a hardcoded single-name path (prelude only,
 pre-prep.3) to a flag-driven multi-module mechanism (since
 prep.3 of `kernel-extension-mechanics`). The loader at
 `crates/ailang-surface/src/loader.rs::load_workspace` injects
-`parse_prelude()` and `parse_kernel_stub()` programmatically,
+`parse_prelude()` and `parse_raw_buf()` programmatically,
 then derives the implicit-imports list from
 `modules.values().filter(|m| m.kernel)`. Every module in the
 workspace's modules map that carries `kernel: true` enters the
@@ -231,8 +232,8 @@ Prelude carries `kernel: true` in `examples/prelude.ail`. Its 12
 free fns (see `examples/prelude.ail:85-148`) remain callable bare
 in every consumer module — ratified by
 `crates/ail/tests/prelude_free_fns.rs` across the code-path
-migration. The ratifying stub kernel module
-(`crates/ailang-kernel/src/kernel_stub/`) and any future kernel-tier
+migration. The `raw_buf` base-extension kernel module
+(`crates/ailang-kernel/src/raw_buf/`) and any future kernel-tier
 consumers (Series, Matrix) auto-import through the same filter.
 
 Class-method dispatch (a separate mechanism — see