Release: enforce the #134 compatibility matrix and README removal gate

Parent: #134 Depends on: #135, #136, #137, #138, #139, #140, #141, #142, #143, #144, #145, and #146 Final README deletion: #246

Goal

Make completion of the roadmap a machine-verifiable release property.

Acceptance

• Check in a compatibility matrix for OS, architecture, public JSC target, private ABI profiles, Objective-C bridge, inspector, WebAssembly profiles, GC modes, JIT tiers, and PR-249 execution.
• Aggregate terminal normal, no-GIL, stress, leak, sanitizer/TSan, differential, bridge, ABI, inspector, Wasm, GC, and JIT evidence for every declared target.
• Fail verification for unexplained skips, stale inventories, missing artifacts, unsupported partial behavior, and generated README drift.
• Regenerate final README capability and benchmark claims from the last committed evidence batch.
• Remove the What Is Not Implemented section only when every declared gate is green (#246).

Current matrix

9e51e1ff raises the checked matrix to 10/12 green gates by completing the optimizing-JIT gate (#146/#434). The remaining open gates are exact and linked:

• #446 — publish shared/mid-script automatic compaction evidence;
• #447 — make the multi-age nursery moving.

The optimizer inventory is CI-gated and separates its complete correctness matrix from the dated ten-kernel JavaScriptCore performance artifact. The matrix verifier also validates the complete 259-executable PR-249 artifact without rerunning its deliberate full reproduction.

WebAssembly compatibility evidence is now available as a machine-verifiable release-matrix input in 939dae44: docs/.data/wasm-conformance-matrix.json combines nine terminal profiles, exact pins/converters, feature and execution-mode dimensions, host/architecture scope, explicit N/A reasons, and 87,838/87,838 applicable passes with zero failures/runner errors. zig build wasm-feature-profiles-check now rejects drift. #147 remains open to aggregate this with ABI, bridge, inspector, GC-mode, JIT-tier, and sanitizer evidence.

Release-gate foundation landed in 54f183f. docs/.data/release-compatibility-matrix.json now declares all required platform/public API/private ABI/Objective-C/inspector/Wasm/shell/GC/JIT/README gates and consumes committed test262 + nine-profile Wasm totals. zig build release-compatibility-check validates artifacts, terminal inventories, README score strings, private-ABI pending state, and the What Is Not Implemented policy. It truthfully reports 4/12 green; zig build release-ready refuses with the eight open gate IDs until every gate is green.

README/release presentation remains compact (77 lines / 491 words) and the published comparison still points to the latest accepted July 17 artifact and 1,540 raw samples. #246 continues to enforce retaining the warning until the release matrix is genuinely green; ongoing ABI work is documented under its versioned profile docs rather than bloating the landing page.

The moving/compacting GC release gate is now terminal: #333–#352 and #144 are closed, committed fragmentation evidence reports 90.8% less retained backing with a 0.99 ms median pause and unchanged post-action throughput, and descendant full CI has 42 successes / one intentional nightly skip / zero failures: https://github.com/zig-utils/zig-js/actions/runs/29716788619. #147 remains open for the still-pending ABI, Core 3/post-MVP, PR-249, multi-age/parallel-minor, and optimizing-JIT gates.

WebAssembly release gate is now green in 6c182abe: ten terminal profiles, 151,802/151,802 applicable commands, 2,862 explicit N/A, zero failures/runner errors, exact source/converter pins, supported-host scopes, and bounded/full-run CI boundaries. The unified release matrix is now 5/12 green; remaining blockers are outside the completed Wasm scope.

Compatibility matrix update 871c2245: moving/compacting GC and multi-age/parallel-minor GC are now green from committed relocation/compaction and 112-row generation evidence. Matrix status advances to 7/12 green; private ABI remains 124 pending.

Platform matrix gate update pushed to main.\n\nCommits:\n- a5f3f69 fix(test262): fail aggregate conformance errors\n- e8319ec chore(platform): publish release support matrix\n\nWhat changed:\n- Added docs/platforms.md plus docs/.data/platform-release-matrix-2026-07-28.json generated by tools/platform-release-matrix.py.\n- release-compatibility now validates the generated JSON/Markdown, CI workflow coverage, benchmark evidence, and platform_scope drift.\n- platform_matrix is now green; README open-gate notice dropped the platform-publication blocker.\n- Test262 parent now exits non-zero on aggregate parse/runtime/host/negative/skip counts, and the finite TypedArray copyWithin coerced-values cluster gets the existing slow worker timeout budget.\n\nVerification:\n- zig build test262 -Doptimize=ReleaseFast --summary failures => VALID 48,506/48,506; NEGATIVE 4,669/4,669; skipped 0\n- ./zig-out/bin/test262 --list-excluded => total 0\n- ./zig-out/bin/test262 --list-skips => total 0\n- ./zig-out/bin/test262 --diag test/built-ins/TypedArray/prototype/copyWithin => 0 fail, 65 pass\n- zig build release-compatibility-check --summary failures => 8/12 gates green; private ABI pending=0\n- python3 tools/platform-release-matrix.py\n- python3 tools/release-compatibility.py\n- bun run docs:build\n- git diff --check\n\nCases flipped: 0

Matrix checkpoint from f6f8ef1b: 9/12 gates green. #143/#430 are complete with a CI-verified 259-executable PR-249 artifact. Remaining gates are now exactly #446 (automatic compaction evidence), #447 (moving nursery), and #434/#146 (optimizer backend/differential evidence). The generated README notice reflects only those three blockers.

Optimizer release evidence in 9e51e1ff advances the generated compatibility matrix from 9/12 to 10/12 green. The only remaining gates are #446 automatic shared/mid-script compaction evidence and #447 moving nursery; final claim regeneration and #246 remain intentionally unchecked until both land.