Interactive command bar (vim-style `:`) for live session control

[karava]

Idea

Build on the live hotkeys (PR #30) with a vim-style command bar: press : during a running session to open an input line, type a command like channel jazz or mascot off, and hit Enter to apply — without leaving the session. Hotkeys cover the common toggles; the command bar adds discoverable, typed commands with arguments (especially picking a specific channel rather than just cycling with n).

UX

• : opens an input field (a dim prompt line); Esc cancels, Enter submits.
• The countdown keeps running; on submit/cancel the bar closes and the countdown resumes.
• Tab-completion / showing valid options would be a nice later touch (e.g. channel names).

Commands to support (initially)

• channel <name> — switch to a named channel (validates against the loaded list)
• mascot on|off, voice on|off
• volume <0-100>
• pause / resume
• maybe work <min> / break <min> to retune mid-session (later)

Where it hooks in

• Reuses the live-input layer from PR Add live hotkeys to control a running session #30 in src/commands/start.ts (raw-mode keystroke handler + the mutable channel / mascot / voice / volume state + setVolume/restartMusic/heartbeat plumbing). The hotkey actions and command handlers should share the same underlying functions (cycleChannel/adjustVolume/etc. → generalize to setChannel(name) / setVolume(n)).

The one real consideration: rendering

Hotkeys today print a dim status line and let the countdown resume below (a scrolling log). A persistent input field needs a small 2-row layout — the live countdown on one row and the command bar on another — so typing into the bar doesn't fight the 1s \r redraw. This means:

• A "suspend the tick redraw → run a mini line-editor → resume" path while the bar is open (handle backspace \x7f, Esc, arrows, Enter ourselves in raw mode).
• Cursor positioning within the alt screen (we already own it from Full-screen session via the terminal alternate screen buffer #20), respecting the width-aware single-line rendering from Progress bar reprints every tick in narrow terminals (tmux splits) — line wraps past \r #14.

This is the layout work intentionally deferred from the hotkey MVP.

Shared benefit

The same suspend-redraw + line-editor mechanism is exactly what #17's in-session feedback hotkey needs (type a message mid-session without leaving). Building the command bar's input layer should make #17's hotkey mostly free.

Constraints (per existing conventions)

• Best-effort and cosmetic-adjacent: never affect timer accuracy or crash a session.
• TTY-only (raw mode); piped/non-interactive sessions just don't offer it.
• Keep the greyscale/compact aesthetic.

Acceptance

• : opens a command bar; Esc cancels, Enter submits, countdown unaffected.
• channel <name>, mascot on|off, voice on|off, volume <n>, pause/resume work and share the hotkey code paths.
• Invalid input shows a brief error and doesn't break the session.
• No redraw/wrap artifacts in narrow terminals (respects Progress bar reprints every tick in narrow terminals (tmux splits) — line wraps past \r #14).

Refs

• PR Add live hotkeys to control a running session #30 (live hotkeys — the input layer this builds on)
• Optional animated pixel-art character running alongside the progress bar (toggleable) #15 (mascot), Progress bar reprints every tick in narrow terminals (tmux splits) — line wraps past \r #14 (width-aware redraw), Full-screen session via the terminal alternate screen buffer #20 (alt-screen takeover)
• In-CLI feedback / bug reporting (devflow feedback + in-session hotkey, no browser) #17 (in-session feedback hotkey — shares the suspend-redraw/line-editor mechanism)