chore: add mise run release task for cutting releases

[alexo-bunnyshell]

Summary

Adds a reusable release helper so cutting a release is a single, validated command instead of a hand-typed gh release create.

mise run release              # cut cli-v<version> from package.json
mise run release -- --dry-run # preview: shows the tag + extracted notes, creates nothing

What it does

scripts/release.sh:

1. Derives the version from package.json → tag cli-v<version>
2. Validates preconditions and aborts with a clear message otherwise:
   • on main, working tree clean, in sync with origin/main
   • src/version.ts matches package.json
   • a ## [<version>] section exists in CHANGELOG.md
   • the tag doesn't already exist (local or remote)
3. Extracts the release notes from that CHANGELOG section (header stripped)
4. Creates the cli-v<version> GitHub release, which triggers publish.yml (binaries + npm)

It deliberately does not bump the version — that stays in the feature PR (package.json / version.ts / CHANGELOG), matching how 0.3.0 was done.

Notes

• Wired as a mise task ([tasks.release] in mise.toml), consistent with the bun pin added in 0.3.0.
• --dry-run verified locally; the precondition checks correctly block a dirty tree / out-of-sync main.

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