feat(parser): implement unambiguous module parsing for JS/TS files

[Boshen]

Summary

• Implements speculative/unambiguous parsing for .js, .jsx, .ts, and .tsx files
• Instead of assuming module or script upfront, parses with ModuleKind::Unambiguous and upgrades to module mode when ESM syntax is detected
• ESM indicators: import, export, import.meta (NOT top-level await alone)
• Defers top-level await errors until module type is resolved
• Vue loader upgrades unambiguous scripts to module mode
• Updates linter tests to use explicit ESM extensions (.mjs/.mts) where needed

Test plan

• All parser tests pass
• All linter tests pass
• All semantic tests pass
• Coverage conformance tests updated

🤖 Generated with Claude Code

[Copilot]

Pull request overview

This PR implements unambiguous module parsing for JS/TS files by deferring module type determination until ESM syntax is detected. Instead of assuming module or script mode upfront, the parser now uses ModuleKind::Unambiguous for .js, .jsx, .ts, and .tsx files, upgrading to module mode only when encountering import, export, or import.meta (notably excluding top-level await alone). The parser defers top-level await errors until the module type is resolved.

Changes:

• Added deferred error handling for script-only syntax violations in unambiguous parsing mode
• Updated parser to upgrade unambiguous mode to module/script based on detected ESM syntax
• Modified linter test file extensions to use explicit ESM extensions (.mjs/.mts/.jsx) where needed

Reviewed changes

Copilot reviewed 296 out of 314 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
crates/oxc_parser/src/lib.rs	Adds deferred script error tracking and module type resolution logic
crates/oxc_parser/src/error_handler.rs	Implements error_on_script method for deferring script-only errors
crates/oxc_parser/src/js/statement.rs	Defers await expression errors in for-await statements
crates/oxc_parser/src/js/expression.rs	Defers await expression errors and fixes regex detection after await
crates/oxc_semantic/tests/fixtures/*	Updates test snapshots removing StrictMode flag from unambiguous files
crates/oxc_linter/src/snapshots/*	Updates linter test snapshots with corrected file extensions

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[codspeed-hq]

CodSpeed Performance Report

Merging this PR will not alter performance

_{Comparing feat/unambiguous-module-parsing (e1c205d) with main (6ec08e8)¹}

Summary

✅ 42 untouched benchmarks
⏩ 3 skipped benchmarks²

Footnotes

1. No successful run was found on main (01d7b13) during the generation of this report, so 6ec08e8 was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩

2. 3 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

[Boshen]

Merge activity

• Jan 17, 1:36 PM UTC: The merge label '0-merge' was detected. This PR will be added to the Graphite merge queue once it meets the requirements.
• Jan 17, 1:39 PM UTC: Boshen added this pull request to the Graphite merge queue.
• Jan 17, 1:46 PM UTC: Merged by the Graphite merge queue.