TypeScript parity: reach 100% exact conformance and a green TS suite

[chrisbbreuer]

Objective

Reach full logical parity with the TypeScript reference implementation in ~/Code/typescript-go: every TypeScript unit, integration, compiler, and exact conformance test passes without fixture-specific hardcoding.

Authoritative gates

• ts_checker is fully green with zero failures or crashes.
• ts_conformance coarse mode remains 5,907 / 5,907.
• ts_conformance exact mode reaches 5,907 / 5,907 byte-for-byte baselines.
• Remaining TypeScript package tests (ts_parser, ts_program, ts_driver, ts_resolver, emit/declaration tests) are green.
• Full repo test gate has no TypeScript-related failures.
• README, capability matrix, and parity plan report one consistent verified count.

Current verified state

As documented at HEAD before this tracking issue was opened:

• Coarse conformance: 5,907 / 5,907 (100%).
• Exact conformance dashboard: 4,220 / 5,907 (~71.4%), with 1,687 fixtures remaining.
• ts_checker: 2,974 / 3,006 pass, 30 fail, 2 crash after the callable-object/arity parity wave; the two crashes are existing conditional-distribution invalid-TypeId failures.

Exact parity is the completion criterion. Diagnostic-code reachability alone is not proof of parity.

Working rules

• Port semantics from TypeScript/tsgo, not fixture names or expected text tables.
• Land small conventional commits with focused regressions and exact-corpus evidence.
• Record each verified fixture/window delta in linked issues and comments.
• Keep child issues linked here and close them only when their stated gate is proven.

References

• docs/TS_PARITY_PLAN.md
• docs/TS_DIAGNOSTIC_REACHABILITY.md
• docs/TS_DIAGNOSTIC_CODE_STATUS.md
• packages/ts_conformance/

[chrisbbreuer]

Opened parserharness workstream #68 and landed the first tracked exact-parity chunk in 26f794917.

Dashboard movement for this chunk: one exact diagnostic row fixed; ts_checker moves from 31 to 30 known failures at 2,974/3,006 pass, with the two existing conditional-distribution crashes still open. Exact fixture totals remain 4,220/5,907 because parserharness still has other mismatches and therefore has not flipped from failing to passing.

[chrisbbreuer]

Opened checker workstream #69 and pushed 5ed86afd3.

ts_checker is now crash-free at 2,976/3,006 pass, 30 fail, 0 crash. This flips the two existing conditional-distribution crashes to passes by fixing union-member slice ownership during recursive interning.

[chrisbbreuer]

Enum assignment parity is now exact across the focused cluster: 9f04059c0 flips enumAssignmentCompat5, moving enumAssignmentCompat* from 6/7 to 7/7. Full checker: 2,978/3,007 passing, 29 known failures, zero crashes.