ABI: define and implement versioned Bun and Home private-JSC profiles

[chrisbbreuer]

Parent: #134
Depends on: #135
Public JavaScriptCore C-API compatibility remains separate from these private shims.

This issue replaces vague private-ABI claims with exact, auditable Home and Bun compatibility profiles.

Acceptance

• Inventory concrete Home and Bun revisions and every required symbol, layout, calling convention, provider, and semantic assumption.
• Implement both complete profiles with generated symbol/layout/provider verification.
• Reject unknown, mismatched, or drifted revisions explicitly.
• Add independently compiled compile-link-runtime fixtures for each pinned consumer.
• Keep public C-API compatibility separate from private ABI shims.
• Reach zero missing and zero unclassified entries for every declared profile.
• Run private fixtures in Debug, ReleaseSafe, and TSan and gate sanitizer propagation in CI (CI: propagate TSan to private ABI consumer fixtures #423).

Declared profiles

• ABI: implement the pinned Home private-JSC profile #163 — Home 7ed99c02e50034f869d0db6d487115bb44332fe4: 447/447.
• ABI: implement the pinned Bun private-JSC profile #164 — Bun 4982b91e3702094330f3be3883354c52b8c01323: 437/437.
• ABI: classify the remaining Bun-owned private profile exports #422 — consumer-owned provider classification and final-link audit.
• CI: propagate TSan to private ABI consumer fixtures #423 — complete private-fixture TSan propagation gate.
• ABI: implement retained exception SourceProvider lifecycle #424 — retained exception SourceProvider lifecycle.

All historical implementation children are closed. Exact main commit e3fdc52385204c75fe6ae5c64d48dae6e5ede418 passed all 43 Actions jobs.

[chrisbbreuer]

Profile work is now structurally separated. #162 completed the pinned Home public-C consumer at 50/50 symbols (b5d131b, 8b329a2); it does not count toward private compatibility. Private Home and Bun implementations remain tracked by #163 and #164.

[chrisbbreuer]

Home private inventory child #165 is complete (20228d6, 4ae1d42). The exact pinned source denominator is 448 unique externs: 432 genuine private entries still pending under #163, 15 public-C overlaps, and one platform import; zero duplicates/unclassified. This is inventory evidence only, not a private compatibility claim.

[chrisbbreuer]

First real private implementation slice is complete: #166 added the exact JSC64 boundary, and #167 now exports 4/432 Home private symbols with runtime evidence. The pinned Home profile has 428 private entries remaining; public and private counts remain mechanically separate.

[chrisbbreuer]

Bun core inventory #169 is complete: 437 src/jsc symbols, 422 private (4 implemented / 418 pending), 15 public overlap. Exact comparison proves the profiles differ: 3 Bun-only, 14 Home-only, and 28 changed signatures among 434 shared names.

[chrisbbreuer]

Shared Home/Bun child #170 is complete. The exact JSC64 BigInt bridge adds three real context-owned cell shims and advances the pinned inventories to Home 7/432 and Bun core 7/422 without changing the 117 public functions or 19 extensions. Commits: 46ccb1f and 3c53b3e.

[chrisbbreuer]

Shared equality child #171 is complete. Exact strict and SameValue shims advance Home to 9/432 and Bun core to 9/422, with semantic coverage for NaN, signed zero, strings, BigInts, object identity, sentinels, and foreign contexts. Public/extension counts remain 117/19. Commits: 9538d72 and f5e54f4.

[chrisbbreuer]

Profile-selectable JSType child #172 is complete. The exact source inventories prove 97 Home tags versus 98 Bun tags, with one Bun-only insertion and 70 renumbered shared members. Both separately compiled profiles pass 2/2 signatures across 20 real cell kinds. Home advances to 11/432 and Bun core to 11/422; public/extension totals stay 117/19. Commits: 74d461f and 6a6657f.

[chrisbbreuer]

Home revision-alias child #173 is complete. Current Home 38702f9e is accepted only through its own manifest after proving all 58 JSC source hashes and all 448 declarations unchanged from the immutable base; requesting that checkout under the older alias is rejected. Commits: 17e6532 and 7f9d2b5.

[chrisbbreuer]

Shared BigInt-cell child #174 is complete. Five exact opaque-cell shims add arbitrary-precision i64/u64/f64 ordering and signed modulo extraction, advancing Home to 16/432 and Bun core to 16/422 with public/extension totals unchanged at 117/19. Commits: f18d0d7 and 0b81e97.

[chrisbbreuer]

Shared JSCell/JSString child #175 is complete. Seven exact symbols add UTF-16/WTF-8 length, 8-bit eligibility, equality, object access, primitive boxing, and foreign-context rejection. Home advances to 23/432 and Bun core to 23/422; public/extension totals stay 117/19. Commits: 379ed5d and 70b2a2e.

[chrisbbreuer]

Shared object-foundation child #176 is complete. Three exact symbols add fresh ordinary/null-prototype construction and exact Number/String/Boolean/BigInt wrapper unboxing. Home advances to 26/432 and Bun core to 26/422; public/extension totals remain 117/19. Commits: 06ec44c and 1c4f5ec.

[chrisbbreuer]

Shared BigInt comparison/arithmetic child #177 is complete in aa3828f and 24626fb. Home is now 29/432 and Bun core 29/422; the profile parents remain open for their pending inventories.

[chrisbbreuer]

Shared ToObject/prototype child #178 is complete in dacec16 and a2024aa. Home is now 31/432 and Bun core 31/422; both profile parents remain open for their pending inventories.

[chrisbbreuer]

Shared numeric DateInstance child #179 is complete in 6bdec54 and f2e55b6. Home is now 33/432 and Bun core 33/422; parsing/timezone/ISO-buffer contracts remain pending separately.