Smarter editing & broader file support

Lists, code blocks, and text files all get meaningfully better handling, with new keyboard shortcuts to match.

Smart list indentation — press Tab / Shift-Tab inside a Markdown list to indent or outdent the item, keeping markers and nesting tidy.
New keyboard shortcuts — ⌘⇧T toggles a task checkbox, ⌘. copies the note's relative path, and ⌘⇧, copies its absolute path.
Broader file support — plain .txt files now open as Markdown notes, and developer files (.swift, .json, .yaml/.yml, .toml, .sh, .zsh, .xml, .plist, .env, Makefile, Dockerfile) open in source mode with syntax highlighting.
200 folder icons — the icon picker catalog has been expanded significantly, with aliases so you can find the right symbol faster.

Indented code blocks — fenced code blocks inside list items and blockquotes now highlight and preview correctly.
Inline code rendering — better font sizing and baseline alignment in preview.
List spacing in preview — tighter, more consistent vertical rhythm for nested and mixed lists.

Opening a file externally now reliably surfaces or reopens the correct window instead of doing nothing.
Sidebar selection only scrolls into view when it is actually offscreen, eliminating unnecessary jumps.