Profile and reduce fresh-runtime TypeScript compiler latency (GOL-347)

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Summary

• add feature-gated, phase-level execution and bounded module/filesystem counters for fresh-runtime TypeScript compiler profiling
• replace default path-based readFileSync chunk loops with one private native whole-file read while preserving fd and custom-flag fallbacks
• publish paired schema-v5 P2/P3 reports, focused compatibility coverage, and measured follow-up dispositions

Why

Fresh QuickJS TypeScript compiler jobs spent material time crossing the JS/native boundary for 8 KiB file reads. The controlled profile identified TypeScript import as the selected owner: 1,453 native reads became 68 whole-file reads for the same 10,961,854 bytes.

Five-sample controlled A/B medians:

Target	Wasm wall	TypeScript import
P2	22.896 s → 20.306 s (-11.31%)	9.626 s → 7.370 s (-23.44%)
P3	22.871 s → 20.291 s (-11.28%)	9.629 s → 7.372 s (-23.44%)

Compatibility

• ordinary execution remains unprofiled; typescript-compiler-profiling is enabled only for the Agentic TypeScript component
• readFileSync retains Buffer/string behavior, malformed UTF-8 handling, URL and Buffer paths, fd/custom-flag fallback, and Node-compatible ENOENT/EISDIR metadata
• queued job lifecycle totals include queue delay and are validated for concurrent compiler/CPU/I/O jobs
• GOL-348, GOL-349, and GOL-350 remain separate measured follow-ups; GOL-351 remains folded because its hypothesis did not meet the materiality gate

Validation

• current paired schema-v5 P2/P3 report validation
• five-sample P2/P3 profiling smoke and clean report regeneration
• focused P2/P3 fs_read_file_sync_fast_path runtime coverage
• P2/P3 Node compatibility test_fs_readfile family
• exact Agentic TypeScript and fs DTS goldenfile tests
• focused development-profile contract test
• formatting and failure-safe default/maximal skeleton Clippy matrix
• independent Codex and Claude correction-delta reviews

Stack

This draft targets gol-421-skeleton-clippy because the profiling work depends on that branch's skeleton/module-loading source state. The base PR's known Rust 1.98 DES3 CBC Clippy correction remains independently gated.

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Exact candidate: ca96cac7800089062826532ebb337f57554bec35.

Correction-delta review is closed:

• Codex: clear; all four original findings resolved.
• Claude: clear; all ten correction obligations confirmed. Four low-severity, non-blocking follow-up observations were recorded (feature-label deduplication, two report mutation guards, an uncertain UTF-8 error-path nuance, and a pre-existing custom-flag directory-read divergence).

Independent exact-SHA validation passed:

• formatting and paired P2/P3 report currentness
• exact Agentic TypeScript and fs DTS tests
• P2/P3 focused fs_read_file_sync_fast_path
• P2/P3 17-case Node readfile family and dedicated readFileSync filters
• development-profile semantics
• P2/P3 default and maximal failure-safe skeleton Clippy lanes

The tracked tree remained clean and the skeleton manifest/artifact cleanup contract was restored after validation.

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CI classification for exact head ca96cac7800089062826532ebb337f57554bec35:

• build passed and the full matrix was admitted.
• skeleton-clippy failed only at the stacked base's two known Rust 1.98 clippy::chunks_exact_to_as_chunks diagnostics in src/builtin/web_crypto.rs:680 and :700.
• The failure is outside the GOL-347 diff and matches the independently recorded GOL-421 authorization gate; no GOL-347 diagnostic appeared.

Remaining exact-SHA CI jobs continue to run. The branch will not absorb a third-cycle GOL-421 correction without the required authorization checkpoint.