chore(todo): disable todo feature pending listing / search / edit flows
The two cmd-panel commands wired in `feat(todo)` work but aren't
useful day-to-day without:
- a `todos` listing/search UI in the cmd panel (vs. opening the
tags grid and filtering by #todo manually)
- tab/down autocomplete that suggests existing todos as you type
`done …`
- an inline edit affordance from the suggestion list
Disabled by renaming `features/todo/manifest.json` →
`manifest.json.disabled` so `discoverFeatures()` skips the directory.
The handlers and tile boilerplate stay checked in. README.md in the
feature dir explains why and how to re-enable when the missing
flows land.
No code changes — the feature picks up automatically on next app
start once the manifest is renamed back.