feat: support prerelease publish tags

[huntharo]

Summary

• add shared release tag parsing and metadata output for stable and prerelease tags
• publish all packages with the correct npm dist-tag and validate GitHub prerelease state
• document prerelease release creation in the local release skill

Verification

• node --test scripts/release-tag.test.mjs
• node ./scripts/release-metadata.mjs v0.7.0
• node ./scripts/release-metadata.mjs v0.7.0-beta.1
• pnpm typecheck

[github-actions]

Cluster Performance

• Status: PASS
• Fixture median: 442.9 ms (12 samples, 3 cluster rebuilds/sample)
• Fixture baseline: 535.1 ms
• Fixture delta: -92.2 ms (-17.2%)
• Projected openclaw/openclaw duration: 8m 16.6s
• Projected openclaw/openclaw baseline: 10m 0.0s
• Projected delta: -103436.4 ms (-17.2%)
• Regression threshold: +50.0%
• Fixture shape: 512 threads x 3 source kinds
• Sample durations: 458.1 ms, 456.6 ms, 443.4 ms, 450.3 ms, 455.3 ms, 442.3 ms, 437.3 ms, 435.6 ms, 455.5 ms, 438.3 ms, 436.6 ms, 435.2 ms

Run: workflow run for 09f2ce8