Port bun:jsc heapStats mimalloc aggregate and dump corpus

Scope

Activate the byte-identical js/bun/jsc/heapStats-mimalloc.test.ts corpus.

The four upstream tests validate:

• real mimalloc version, pages, committed memory, and malloc bins
• per-heap page dumps
• per-block ids and sizes
• well-formed dumps after a Bun.Transpiler allocation path

Baseline

The exact file is currently rewritten to one native todo:

• 0 pass
• 0 fail
• 0 unsupported
• 1 todo

The corpus file is byte-identical to ~/Code/bun. The real home-debug runtime already exposes native mimalloc aggregates and dump data; only the corpus harness bun:jsc module is stubbed.

Acceptance

• Preserve upstream byte identity.
• Bridge this corpus to real home-debug bun:jsc.heapStats output; do not synthesize mimalloc values.
• Preserve aggregate, pages-only, and blocks dump modes.
• Run all four upstream tests and add a permanent unchanged-corpus regression.
• Avoid changing lightweight heapStats behavior for unrelated corpus files.
• Pass the exact file and full home_test gate.
• Commit and push as Chris Breuer with no coauthors.
• Link completion to #66.

Implemented and pushed in e601d18 (feat: port Bun mimalloc heap statistics).

What landed:

• activated the byte-identical upstream js/bun/jsc/heapStats-mimalloc.test.ts corpus (verified with cmp)
• exposed in-process native callbacks for the same linked mi_stats_get_json and mi_heap_dump_json APIs used by Home/Bun’s native bun:jsc implementation
• preserved real aggregate mimalloc counters, per-heap/per-page dumps, and the complete per-block dump; no fabricated values, truncation, reduced samples, or subprocess snapshot replay
• matched upstream debug/release address handling and scoped the richer bridge to this corpus so unrelated lightweight heapStats() consumers remain unchanged
• added a permanent home_test regression requiring all four upstream tests to pass with zero todo/unsupported

Validation:

• ./pantry/.bin/zig build debug --summary failures — pass
• exact corpus — 4 passed, 0 failed, 0 unsupported, 0 todo
• ./pantry/.bin/zig build test -Dfilter=home_test --summary failures — pass

Closing as complete. Tracking continues in #66.