feat(parser): report spec parse errors via recoverable_errors

[Boshen]

Closes #86.

Problem

Since the css-syntax conformance work (#61), the parser recovers from EOF/newline-unclosed constructs to a valid AST but records nothing in recoverable_errors(). The recovery is spec-conformant, yet the spec labels each of these "this is a parse error", so downstream consumers (oxc_formatter_css) cannot tell recovered-from-broken input apart from valid CSS — and end up formatting it into corrupted, non-idempotent output.

Change

Record these spec parse errors. Purely additive — the AST and recovery behavior are unchanged, so css-syntax conformance is unaffected (same mechanism as the existing TopLevelDeclaration recoverable error).

New ErrorKinds and where they're recorded (two sites cover every case):

Kind	Case	Site
EofInBlock	{}-block closed at EOF (style-rule and at-rule blocks)	SimpleBlock::parse
UnterminatedString (reused)	string closed by EOF — spec's canonically-closable <string-token>	parse_declaration_value_tokens
BadString	string closed by a newline — <bad-string-token>	parse_declaration_value_tokens
UnclosedParen	(/[ group closed at EOF in a raw value	parse_declaration_value_tokens

Every other unclosed-construct context (@import "…, a[href="…, @media (…) already hard-errors, so these are the only silent-recovery paths.

BadUrl from the issue's "e.g." list is not applicable: this parser models url(…) as a flexible function rather than emitting spec bad-url-tokens, so there was never a silent bad-url recovery to convert.

Verification

• All parser tests pass; cargo fmt + clippy clean.
• wpt css-syntax conformance unchanged (5 clean / 2 expected) — spec conformance genuinely unaffected.
• Conformance flips 10 plain-.css fixtures in the dialect suites (sass-spec, less.js) from clean → recovered; each is a genuine malformation (e.g. a sass output.css with a stray output: ";, and a truncated less.js actual.css ending mid-base64). Snapshots regenerated.
• Moved 3 now-legitimately-recovering fixtures out of tests/ast/ (which asserts no recoverable errors) into tests/recoverable/eof/, and added fixtures/snapshots covering every kind.

🤖 Generated with Claude Code

[codspeed-hq]

Merging this PR will not alter performance

✅ 4 untouched benchmarks
⏩ 1 skipped benchmark¹

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_{Comparing report-spec-parse-errors (ef585f0) with main (e4c405e)}

Footnotes

1. 1 benchmark was skipped, so the baseline result was used instead. If it was deleted from the codebase, click here and archive it to remove it from the performance reports. ↩

[chatgpt-codex-connector]

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