chore(release): v0.6.0

[slgoodrich]

Release commit for v0.6.0. CHANGELOG entry was added in #112 and is already in place with today's date (2026-04-30).

What landed in v0.6 (per CHANGELOG.md `[0.6.0]`)

Added

• `input: 'string'` and `inputFile` accepted on execa
• `stdin: 'string'` stored in cassettes and matched on tinyexec
• `node: true` and `execaNode` named export accepted on execa
• `lines` object form (`{ stdout, stderr, all, fd1, fd2 }`) supported in execa synthesize
• `BinaryInputError` class for non-UTF-8 `inputFile`
• stdin included in `defaultCanonicalize` (with redaction round-trip)
• stdin redaction via the same pipeline as args/stdout/stderr (`RedactSource` extended)
• ReplayMissError hint when the failing call passed `node: true`
• Compile-time exhaustiveness over `RedactSource` at every parallel-arm site
• `useRecordingEnv()` test helper

Changed

• `REVIEW_WARNING` text drops `stdin` from the not-redacted list
• `defaultCanonicalize` includes stdin
• `RunnerHooks.buildCall` is now async (internal API; users importing only the high-level entries are unaffected)
• `wrapFsError` extracted in `src/io.ts`
• "Tracked in backlog" phrases dropped from validator and runtime error messages

Notes

• Cassette schema stays at version 2; v0.5 cassettes load with `stdin: null` and continue to match calls without an input option
• Double-read of `inputFile` (us + real execa) is documented and tracked for v0.7 optimization

Test Plan

• `npm run lint`
• `npm run typecheck`
• `npm test`
• `npm run build`