feat(files): also search the home folder with Spotlight on macOS

[jewei]

What changes

From the comparison with bopop. Decisions: off by default, home folder only, names only.

• Settings > Files > Also search with Spotlight (macOS only, spotlightFiles, default off).
• Files tab, two steps: the index answers at once as before; then a new command spotlight_files asks Spotlight, and the launcher appends its results (its own latestOnly queue, for the same input only; a failure changes nothing). From 2 characters.
• platform::find_files: macOS runs /usr/bin/mdfind -onlyin <home> -name <query> with fixed arguments (no shell), reads at most 100 paths, and stops after 1 second. Windows and Linux return nothing.
• spotlight.rs: drops paths the index already has, and paths that a scan would skip (files::lists: hidden, dot names, skipped folder names, inside packages). It ranks by the same name matcher.
• Safety: State::found keeps the 500 paths Spotlight returned most recently; Open and Reveal accept indexed paths or these (actions::offered_file). The webview still opens only what TinyDash offered.
• Spotlight results have no Pin (files::found_result): a pin resolves through the index.

Measured

mdfind takes 190–450 ms per query on this Mac. That is too slow for every keystroke in All, so only the Files tab uses it, after the index.

Commands run

Command	Result
bun run verify	Pass: 134 frontend tests, build OK, 161 Rust tests
TINYDASH_LIVE_SPOTLIGHT=1 cargo test live_spotlight	Pass: real Spotlight results, all under home, no hidden parts, all remembered

Not checked

The Files tab in the running app (typing needs key presses); the launcher tests cover the merge.