Docs: remove What Is Not Implemented after all release gates pass

[chrisbbreuer]

Parent: #134
Depends on: #147, #140, #141, #142, #143, #144, #145, #146

Track the final, reviewable change that removes the README What Is Not Implemented section after every implementation and evidence gate is genuinely complete.

This is the terminal documentation issue, not a duplicate implementation umbrella: implementation remains in #134 and its children; the compatibility/evidence matrix remains in #147.

Required implementation gates

• Every declared Home and Bun private-JSC profile reaches zero pending inventoried entries, with unknown revisions rejected explicitly.
• The Objective-C bridge and inspector/debugger profiles are complete for their pinned targets.
• WebAssembly and the selected post-MVP feature profiles are implemented and pass versioned upstream inventories.
• Every relevant PR-249 WebAssembly/JIT shell hook is implemented or explicitly dispositioned with no hidden skips.
• Moving/compacting, multi-age generational GC and parallel mid-script minor collection pass relocation, weak-reference, leak, stress, and TSan gates.
• The optimizing JIT includes speculation, deoptimization, OSR, stack maps, invalidation, precise-GC integration, and declared architecture coverage.

Final evidence and README gate

• Release: enforce the #134 compatibility matrix and README removal gate #147 publishes a checked-in compatibility matrix covering exact OS, architecture, ABI, Wasm, GC, and JIT targets.
• Normal, no-GIL, stress, leak, sanitizer/TSan, differential, bridge, inspector, ABI, Wasm, and JIT evidence is green with no unexplained exclusions.
• README benchmark scores are regenerated from the latest committed single-thread, multithread, and JavaScriptCore artifact and clearly separate correctness from speed.
• Unsupported hosts, revisions, or profiles fail clearly instead of exposing partial behavior.
• Remove the section and its table-of-contents entry in one final commit, replacing any still-useful target limitations with links to the versioned compatibility matrix.

Completion rule

Close this issue only after the README no longer needs the warning section because every claim is backed by the exact declared inventories and evidence. No universal-JavaScriptCore claim is implied beyond those named targets.

[chrisbbreuer]

WebAssembly MVP gate progress: #141 and #260 are complete. README.md now removes the upstream MVP inventory/runtime from the missing-surface list and publishes the 16,801/16,801 observable-command score. The remaining WebAssembly README caveat is correctly narrowed to post-MVP profiles and PR-249 WebAssembly/JIT shell hooks; #261 tracks supplemental bit-exact NaN corpus execution. The terminal removal gate remains open for #142/#143 and the private ABI, GC, optimizing-JIT, and compatibility-matrix work.

[chrisbbreuer]

The complete WebAssembly MVP chain #141/#260/#261 is now closed. README evidence is 18,840/18,840 applicable wg-1.0 commands passing with 0 failures/runner errors, and the missing-surface section contains only post-MVP profiles plus PR-249 WebAssembly/JIT shell hooks. #142 and #143 remain the genuine WebAssembly-side removal gates.

[chrisbbreuer]

README removal progress: post-MVP WebAssembly is no longer wholly unimplemented. #262, #269, and #270 are complete; the README now names opt-in sign-extension, saturating conversion, and multi-value support while retaining the remaining-profile caveat. Reference types #271, bulk memory #272, structural score #273, and #264-#268 still block removing that caveat entirely.

[chrisbbreuer]

WebAssembly removal-gate progress: #274 is complete. The runtime now has tagged funcref/externref slots with ordinary and no-GIL precise-GC publication, identity preservation, and exact reclamation after overwrite/drop/unwind. Focused evidence is 145/145 plus a dedicated 3/3 no-GIL filter at e2f01223; README/docs were refreshed in 72bcfad0. The WebAssembly gate remains open for #275, #272, #273 and the later selected profiles.

[chrisbbreuer]

WebAssembly removal-gate update: d2fca189 adds tagged arbitrary externref tables plus JavaScript externref Table/Global identity and exact GC reclamation; focused evidence is now 151/151 with zero skips/failures/leaks. README/docs are current at 7e9417c9. #275 remains open for reference-valued function-call boundaries and final multi-table/cross-instance evidence.

[chrisbbreuer]

WebAssembly removal-gate progress: reference types #271/#274/#275 are complete. The runtime now covers feature-gated reference instructions, multiple typed tables and exact explicit indices, arbitrary externref Table/Global identity and reclamation, canonical reference-valued JS/Wasm calls, mixed multi-value references, and cross-instance indirect calls. Focused evidence is 153/153 at d3736891; the strengthened table-index witness is green at 5374e601; README/docs are current at bfb22343. Remaining WebAssembly gates are bulk memory #272, structural score #273, later profiles #264-#267, and matrix #268.

[chrisbbreuer]

WebAssembly removal-gate progress: bulk memory #272/#276-#278 is complete alongside multi-value and reference types. Focused evidence is 159/159 plus the final cross-instance/precise-GC 3/3 witness; README/docs at 03d46ae9 now list DataCount/passive segments and complete memory/table bulk operations as implemented. The next structural gate is exact profile score #273; later profiles #264-#268 and PR-249 #143 remain open.

[chrisbbreuer]

WebAssembly Core 2 structural evidence advanced: #263 and #273 are now complete. The committed pinned inventory scores 27,437/27,437 applicable commands across 90/90 official wg-2.0 files, with 581 explicit text-format n/a commands and zero failures/runner errors. README/docs are current through 66a953a, and the July 17 1,540-sample single-thread/multithread/JSC benchmark remains current because these paths do not execute in those workloads. This terminal issue remains open: SIMD/Threads/exceptions-tail-calls/memory64-GC, PR-249 hooks, private ABIs, production GC, optimizing JIT, and final matrix gates are still outstanding.

[chrisbbreuer]

README status was refreshed in dfff7df3: Threads is no longer described as unimplemented. The section now names only terminal Threads proposal-script/TSan/scaling evidence under #287, while retaining this issue as the evidence-backed gate for eventually removing the entire “What Is Not Implemented” section.

[chrisbbreuer]

README-removal progress: the WebAssembly Threads proposal-script caveat is now obsolete and was removed in bf258e90. The complete pinned Threads corpus passes 551/551 with zero failures/n/a/runner errors and has a checked-in exact inventory. The broader WebAssembly gate remains open for the other selected post-Core-2 profiles/shell hooks and #287's terminal TSan/scaling evidence; no checkbox is prematurely closed.

[chrisbbreuer]

README benchmark evidence advanced again on main: the new WebAssembly Threads section links the 105-sample raw/report artifact, presents 1/2/4/8-worker atomic and wait/notify results, preserves the equivalent ordinary-JS and SIMD JSC comparisons, and explicitly records why shared Wasm is N/A in the public system-JSC embedding. The terminal README-removal gate remains open for the broader implementation roadmap and #287 host-wide TSan evidence.