Add root right panel terminals

[ymichael]

Summary

• Add a root-route right panel/drawer with file, browser, and terminal tabs.
• Add top-level terminal APIs and daemon host-path terminal support so root terminals do not require thread environments.
• Wire root New Tab behavior, file search, recents, prompt file/mention pills, and persisted root file-preview tabs with the owner context needed after refresh.
• Stabilize refreshed file previews by waiting for the Pierre worker pool before mounting code previews and remounting once highlighted AST cache is available.

Validation

• pnpm exec turbo run typecheck --filter=@bb/server-contract --filter=@bb/db --filter=@bb/host-daemon-contract --filter=@bb/server --filter=@bb/app --filter=@bb/host-daemon
• pnpm exec turbo run test --filter=@bb/server -- test/public/public-thread-terminals.test.ts
• pnpm exec turbo run test --filter=@bb/host-daemon -- src/terminals/terminal-manager.test.ts test/command/environment-dispatch.test.ts
• pnpm exec turbo run test --filter=@bb/app -- src/views/RootComposeView.test.ts
• pnpm exec turbo run test --filter=@bb/db -- test/data/terminal-sessions.test.ts
• pnpm exec turbo run test --filter=@bb/db -- test/migrate.test.ts
• pnpm exec turbo run test --filter=@bb/server-contract -- test/contract.test.ts
• pnpm exec turbo run typecheck --filter=@bb/app
• pnpm exec turbo run lint --filter=@bb/app
• pnpm exec turbo run test --filter=@bb/app -- FilePreview fixed-panel-tabs-state secondaryPanelTabState useThreadFileTabs RootComposeSecondaryContent
• pnpm exec turbo run typecheck --filter=@bb/cli
• pnpm exec turbo run test --filter=@bb/cli -- thread-open
• git diff --check