ABI: implement exact deep equality and matching

[chrisbbreuer]

Goal

Implement the exact pinned Home/Bun private-JSC structural comparison family:

• JSC__JSValue__deepEquals
• JSC__JSValue__strictDeepEquals
• JSC__JSValue__jestDeepEquals
• JSC__JSValue__jestStrictDeepEquals
• JSC__JSValue__jestDeepMatch

This is a child of #134, #140, #163, and #164.

Required semantics

Shared structural engine

• Preserve primitive SameValue/strict comparison rules, pairwise cycle detection, and failure-atomic traversal.
• Compare enumerable string and Symbol properties with exact ordinary Get/proxy/getter observability and ordering-independent key matching.
• Cover dense, sparse, and accessor Arrays; ordinary/null-prototype/class objects; boxed primitives; functions; and cross-realm prototypes.
• Cover Date, RegExp, Error name/message/cause/enumerables, Map, Set, ArrayBuffer, DataView, every numeric TypedArray, detached/shared backing, and float NaN/signed-zero behavior.
• Preserve strict-mode distinctions for prototypes, missing versus explicit undefined, sparse holes, Error causes/types, and bitwise typed-float comparison.
• Reject invalid or foreign-VM inputs deterministically, publish traversal exceptions, and preserve the first pending exception.

Jest modes and subset matching

• Implement asymmetric matcher dispatch and its exception/callability behavior only for Jest-enabled equality.
• Implement recursive subset matching for jestDeepMatch, including inherited/existing properties, nested object-containing behavior, cycles, and optional replacement of matched properties.
• Keep non-Jest equality free of matcher hooks.

Child issues

• ABI: implement exact core structural equality #230 — core structural engine and non-Jest equality
• ABI: implement exact Jest deep matching #231 — Jest asymmetric equality and subset matching

Completion evidence

• Add focused matrices for primitives, prototypes, arrays/holes, cycles, maps/sets, buffers/views, dates/regex/errors, getters/proxies, Symbols, asymmetric matchers, subset replacement, sibling realms, foreign VMs, and first-wins exceptions.
• Add all five symbols to both pinned inventories and the linkable private-value fixture.
• Keep public/private export classification at zero unclassified symbols.
• Run focused tests during implementation, then one batched Home/Bun/public ABI audit.
• Update README and compatibility documentation with exact counts and evidence.
• Close only after implementation and documentation commits are on origin/main.

[chrisbbreuer]

All five pinned structural comparison exports are implemented and documented on origin/main.

• core engine: 0b025285; core docs: 9d511f93
• Jest layer: 06864e96; Jest docs: 8fc2f925
• focused core and Jest matrices each pass 3/3 with zero leaks
• combined fixture passes 219/219
• Home is 220/431 implemented (211 pending)
• Bun core is 214/421 implemented (207 pending)
• public/private audit remains 117 public, 19 extensions, 224 private/support, zero unclassified

#230 and #231 are both complete. Benchmarks remain at committed artifact 36a617b3, correctly unchanged for this ABI-only family.