feat: configurable search and command palette

[WangEn]

What changed

• add Search Engine create/update/delete API backed by the existing D1 search_engines table
• seed Google, Bing, DuckDuckGo and GitHub with !g, !b, !ddg and !gh
• validate HTTP(S) search templates with a required %s placeholder
• normalize and validate configurable bang keywords
• add a Search Engine management UI with default-engine selection and ordering
• upgrade Launcher into an executable keyboard Command Palette
• support global Cmd/Ctrl+K focus, ArrowUp/ArrowDown selection, Enter execution, Shift+Enter new-tab behavior and Escape clear/blur
• make Workspace and Session results execute Open All / Restore directly from the Launcher
• add default web-search result for ordinary queries
• add bang discovery when typing ! or a partial bang prefix
• add exact bang routing such as !gh dockmark
• update V1 roadmap status

Command priority

Open Tabs > Workspace > Session > Bookmark > Navigation > Search

In Web mode there are no privileged open-tab results yet; the ranking leaves that capability slot ready for the browser bridge.

Search semantics

• ordinary query: local Dockmark matches first, plus the configured default search engine
• !: list configured bang shortcuts
• !gh dockmark: route only to the GitHub search engine
• %s in the configured template is replaced with the URL-encoded query

Validation

CI runs Node 22 install, TypeScript checks and both Web + Extension builds.