Bare /reasoning and /fast now render a native one-tap picker on
picker-capable platforms, with automatic fallback to the text status
card everywhere else — parity with the /model picker UX.
- gateway/slash_commands.py: generic send_choice_picker capability gate
(detected on the adapter type, like send_model_picker); selection and
typed arguments flow through one shared application path so they can
never diverge; choices built from VALID_REASONING_EFFORTS so future
levels appear automatically
- telegram: flat inline-keyboard picker (cp:<idx> callbacks), authorized
users only (same gate as approval buttons)
- discord: ChoicePickerView select menu, auth mirrors ExecApprovalView,
2-minute timeout with expiry edit
- matrix: reaction-based picker; reaction set extended to 12 slots to
fit the full effort ladder + subcommands
- locales: picker_title + choice labels in all 16 languages
- docs: ADDING_A_PLATFORM.md capability table
Closes#61110.