Brummel
50dc478ca5
Resolves Gitea #4. Approach A (atomic single iteration). Six layers in one cohesive cut: CLI `--alloc=gc` arm removed; codegen `AllocStrategy::Gc` variant deleted with the default flipped to `Rc`; libgc link branch removed; ~3 pure-differential e2e tests plus the `gc_stress.ail` fixture deleted; ~9 RC-feature tests that used GC-stdout as backstop lose only the differential assertion (absolute fixed-stdout pin retained); M2 staticlib alloc-guard drops its gc-arm (bump-arm preserved); design/models/rc-uniqueness excises the Boehm-parity-oracle narrative; pipeline.md drops the libgc pipeline-diagram arm; docs_honesty_pin flips from Boehm-present-tense anchor to four absence-pins against Boehm-zombie strings. Three design forks were resolved with the user via brainstorm Q&A: (1) bump survives as bench-floor — `AllocStrategy::Bump`, the `--alloc=bump` CLI flag, and `runtime/bump.c` all stay; the enum keeps two variants (Rc, Bump); the codegen negative-complement test retargets from `AllocStrategy::Gc` to `AllocStrategy::Bump`. Bump's standing role is the raw-alloc bench-floor for RC-overhead measurement, not a production target. (2) the ~12 RC-vs-GC differential e2e tests are NOT all deleted wholesale — pure-differential ones (test name literally `*_matches_gc_*` or `*_same_stdout_as_gc`) are deleted; the RC-feature tests with GC as backstop keep their absolute stdout pin (`assert_eq!(stdout_rc.trim(), "<n>")`) and only lose the differential assertion. This nuance was added at spec time on top of the user's "delete the differential pattern" answer, because the differential was incidental to tests like `rc_box_drop` / `rc_list_drop_borrow` that pin drop-fn correctness under RC and would lose unrelated coverage if deleted entirely. (3) the 1.3× RC-over-bump number is retained in design/models/rc-uniqueness.md but reframed as a bench-health regression gate (not a Boehm-retirement gate); the closure-chain ±15% wider band is preserved analogously. Grounding-check (ailang-grounding-check) PASS — 7 load-bearing assumptions ratified, all spec-named paths and line numbers verified (±2 lines), all proposed-for-removal strings present at the spec-named locations. Assumption #7 (codegen default currently Gc) is structurally self-evident: removing the variant forces the default onto a surviving one by construction. Out of scope, tracked separately: - Gitea #3 "Closure-pair slab / pool" — would tighten the closure-chain ±15% band; not blocked by retirement. - Any further `AllocStrategy::Bump` rework — still a single-variant bench instrument. refs #4