chore: migrate to TypeScript 7

[thymikee]

Summary

Migrate typechecking from the tsgo preview package to the official TypeScript 7 tsc binary.
Use the current typescript@7.0.2 package directly and remove the temporary TS6 compatibility alias because this repo does not need the old compiler API when declaration generation is pointed at the native TS7 executable.
Update tsdown to the latest 0.22.4 release and keep declaration builds on the TS7 native compiler path.

Validation

• Verified latest TypeScript 7 guidance from the official announcement and current npm metadata for typescript, @typescript/typescript6, tsdown, and rolldown-plugin-dts
• pnpm install --strict-peer-dependencies
• node_modules/.bin/oxlint . --deny-warnings
• node_modules/.bin/tsc -p tsconfig.json
• node --experimental-strip-types scripts/layering/check.ts
• node scripts/sync-mcp-metadata.mjs --check
• node_modules/.bin/tsdown

[github-actions]

PR Preview Action v1.8.1
Preview removed because the pull request was closed.
2026-07-08 19:05 UTC

[github-actions]

Size Report

Metric	Base	Current	Diff
JS raw	1.6 MB	1.6 MB	-3.0 kB
JS gzip	508.6 kB	507.7 kB	-850 B
npm tarball	611.7 kB	610.1 kB	-1.6 kB
npm unpacked	2.2 MB	2.2 MB	-5.5 kB

Startup median (7 runs, lower is better):

Scenario	Base	Current	Diff
CLI --version	27.0 ms	26.7 ms	-0.3 ms
CLI --help	55.3 ms	55.7 ms	+0.4 ms

Top changed chunks:

Chunk	Raw diff	Gzip diff
dist/src/logcat.js	+16.3 kB	+5.8 kB
dist/src/internal/daemon.js	-778 B	-169 B
dist/src/tv-remote.js	-502 B	-108 B
dist/src/session.js	-109 B	-39 B
dist/src/registry.js	-26 B	-10 B

[thymikee]

Review finding: this PR migrates the repo from tsgo/no-typescript to TypeScript 7 + tsc, but AGENTS.md still tells agents that the repo typechecks with tsgo, that typescript is not a dependency, and that there is no tsc fallback. That guidance becomes actively wrong after this merges and will steer future tooling/debug work incorrectly. Please update the Toolchain Snapshot in AGENTS.md as part of this tooling migration.

[thymikee]

Addressed the AGENTS.md review comment in 0e7faca7e.

I also checked for remaining legacy TypeScript references:

• First-party stale guidance is gone.
• The only remaining tsgo string is the required upstream rolldown-plugin-dts/tsdown option key used to point declaration generation at the TypeScript 7 native executable.
• The remaining @typescript/native-preview strings are transitive peer metadata in pnpm-lock.yaml, not direct dependencies.

[thymikee]

Review pass on 0e7faca: the earlier AGENTS.md/toolchain guidance blocker is fixed. I rechecked the targeted tooling diff (package.json, tsdown.config.ts, AGENTS.md) and the PR is 22/22 green. No remaining actionable blockers found.