chore: release v4.2.1

[Boshen]

🤖 New release

• oxc_sourcemap: 4.2.0 -> 4.2.1 (✓ API compatible changes)

Changelog

4.2.1 - 2025-09-27

Other

• reduce memory usage by replacing Vec with Box<[Token]>
• replace !0 with INVALID_ID constant for better readability (#175)
• remove outdated comment for TokenChunk

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This PR was generated with release-plz.

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[codspeed-hq]

CodSpeed Performance Report

Merging #176 will degrade performances by 1.74%

_{Comparing release-plz-2025-09-27T13-25-53Z (1a3b969) with main (3e2b510)}

Summary

⚡ 2 improvements
❌ 1 regression
✅ 2 untouched

⚠️ Please fix the performance issues or acknowledge them on CodSpeed.

Benchmarks breakdown

	Benchmark	BASE	HEAD	Change
⚡	generate_lookup_table	1.4 µs	1.3 µs	+2.2%
⚡	to_json	5.7 µs	5.6 µs	+2.09%
❌	add_name_add_source_and_content	1.7 µs	1.7 µs	-1.74%