feat(cli): add stall command for one-shot stall detection

[jongio]

What

Adds a thermoworks stall <SERIAL> command: a one-shot check for whether a cook has stalled, meant for scripts and cron jobs.

It pulls the device temperature history, runs the existing stall detection over it, and reports:

• whether the temperature has plateaued
• when the stall started
• how long it has lasted
• the average plateau temperature

When a stall is active it prints a short wrap suggestion (foil or butcher paper, or hold and wait).

Why

The SDK already ships tested stall detection, and watch --stall-alert shows it live. There was no scriptable, non-streaming way to ask "is this cook stalled right now?" and branch on the answer. This exposes the same detection as a one-shot command, mirroring how temp exposes a single reading for automation.

thermoworks stall M100009168
thermoworks stall M100009168 --threshold 3 --duration 45
thermoworks stall M100009168 --json   # { serial, isStalling, stallStart, stallDuration, avgTemp }

How

• New packages/cli/src/commands/stall.ts maps history readings to the SDK TemperatureReading shape (string timestamps to Date), sorts oldest first, and calls detectStall.
• Wired into src/index.ts (import, stall switch case, help text).
• --threshold and --duration tune the plateau band and minimum duration; defaults match the SDK (2 degrees, 30 minutes).
• Exits non-zero when there is not enough history to assess a stall.

Tests

• packages/cli/tests/stall.test.ts covers arg parsing, active-stall output, the JSON shape, no-stall output, unordered-reading sorting, and the not-enough-history, missing-serial, and not-logged-in exits.
• pnpm --dir packages/cli typecheck, pnpm --dir packages/cli test (887 pass), and pnpm lint are green.

Docs

• Added command sections to packages/cli/README.md and docs/cli-reference.md.

Closes #272