[yuyakinjo]

Summary

• valibot で書いた output.tsx からも outputSchema を出す (これまでは Type.* のみ)
• env.tsx の宣言を _meta["decopin-cli/env"] に載せ、呼ぶ前に必要な環境変数を読めるようにする
• shell.tsx を持つコマンドは tools/list から除外し、名前指定での呼び出しも拒否する（親シェルを変える手段のため、MCP ホスト下では無意味かつ半端に成功して見える）
• choose() を使うコマンドは一覧に残す（失敗が構造化されて返るため）
• ルート名の正規化・切り詰め後の衝突をビルド時・実行時双方でガードする
• README / docs/decisions.md / MCP ガイドに上記を反映

Test plan

• bun test test/runtime/mcp.test.tsx (28 pass)

[github-actions]

Startup benchmark

hello world, 50 warm runs. Both builds are measured in the same
job on the same runner, so the machine cancels out of the comparison.

Build	Mean	Own share
this PR	20.3 ms	16.6 ms
main	20.6 ms	16.8 ms
empty Bun binary (runtime floor)	3.8 ms	—

Difference: -0.2 ms (-1.0%) against main.

Own share is the mean minus the runtime floor — the part this project is
responsible for. CI runners are noisy; read anything under a few percent
as noise rather than a regression.

Bundle size

Minimal CLI (test/fixtures/hello-app: one command, <Line> only),
decopin build --minify. Framework code is all of it, so growth here is
framework growth.

Build	Size
this PR	82.5 KB
main	78.7 KB

Difference: +3.8 KB (+4.9%) against main.
Bytes are deterministic: any difference is real, not runner noise.