fix(parser): support top-level await detection in unambiguous mode

[Boshen]

Summary

• Add support for detecting ES modules via top-level await in unambiguous parsing mode, conforming with Babel's behavior
• In unambiguous mode, when await <expr> is encountered at the top level and the expression is unambiguous, the file is detected as an ES module
• Fixes Script mode parsing where await at top level should always be an identifier

Ambiguous tokens after await (following Babel's isAmbiguousPrefixOrIdentifier())

These tokens don't definitively indicate ESM:

• +, - (unary vs binary operators)
• (, [ (call/member vs grouped expression)
• / (regex vs division)
• % (modulo operator)
• ; (semicolon - empty await)
• Template literals
• of, using (contextual keywords)
• Newlines (ASI boundary)

Results

All 4 Babel TLA unambiguous tests now pass:

• module - TLA with ESM
• ambiguous-script - TLA with ambiguous tokens (Script detected)
• ambiguous-modulo - TLA with % operator
• ambiguous-v8intrinsinc - TLA with V8 intrinsic

Conformance improvements:

• minifier_babel: 100% ✅
• transformer_misc: 100% ✅

🤖 Generated with Claude Code

[codspeed-hq]

Merging this PR will not alter performance

✅ 42 untouched benchmarks
⏩ 3 skipped benchmarks¹

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_{Comparing feat/tla-unambiguous-mode (bf515e2) with main (7cb53ce)²}

Footnotes

1. 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. ↩

2. No successful run was found on main (85903cd) during the generation of this report, so 7cb53ce was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩