2.2.0

• adding release tool, adding copyright header
• feat: arrow key navigation in file picker (down to results, up back to input)
• fix: include filename in search index so file-name queries return results
• fix: abort stale searches, close picker on outside click and file change
• feat: add toolbar file picker to insert markdown links
• feat: drag files from tree into editor to insert markdown link
• feat: navigate to linked .md files on click
• test: document title-case behavior; remove unreachable fallback in titleFromPath
• feat: add file link utilities (titleFromPath, resolveRelative, flattenTree)