Add optional daily summary controls to chat UI

[andesnice]

Summary

• Add an optional daily-summary panel to the chat header. It appears on Windows only when a compatible local companion is installed, and lets the user search, select, and save chats, start a manual summary, and view its status without leaving LINE.js.
• Add cookie-bound /summary/* routes; mutations also require a matching Origin. The server invokes only fixed companion scripts and does not expose child stderr or integration secrets to the browser. The companion, its schedule, and Notion/n8n configuration remain outside this repository.
• Document the companion contract in all three README languages and docs/daily-summary-companion.md. Make the updater test fixture use npm.cmd on Windows and transpile browser test modules so Node 22 builds without native TypeScript stripping can run the suite.

Validation

• npm run typecheck, npm run build, and npm audit --audit-level=high passed.
• node --test test/digest.test.mjs test/update.test.mjs passed (16 tests).
• An isolated Ubuntu/Node 22 checkout from the pushed branch passed all 194 tests and npm audit --audit-level=high.
• On the local Windows installation, authenticated summary selection read/save and rejection of requests without a browser cookie or with a mismatched Origin were verified. The user confirmed the button appears after refreshing the page.
• The full upstream test suite still has nine Windows-specific failures in existing permission, symlink, path, and PWA tests. The real manual-summary action was not repeated during this change to avoid creating another Notion snapshot.
• GitHub Actions currently reports action_required for this fork PR and has not started any jobs; the upstream maintainer may need to approve the workflow before an online CI result is available.