feat: AI-generated daily clockface (LLM picks a theme each morning)

[Ryan4n6]

Idea

Every morning at 6am, a small backend job asks an LLM for a clockface theme based on weather + day-of-week + a seed phrase, generates 64x64 pixel art assets, packages them as a Canvas-compatible JSON theme, and publishes via the auto-update channel (#2). Clock looks different every day.

Why it's interesting

• The Canvas clockface (cw-cf-0x07) already renders a JSON-described theme fetched from a server — the on-device side is mostly free.
• 64x64 pixel art is exactly the resolution where current image models produce charming results.
• Pairs naturally with the manifest auto-update from feat: auto-update from a published manifest (R2-hosted, signed binaries) #2: each morning the manifest URL serves a new theme.

Architecture sketch

Off-device (cron / GitHub Action, runs daily):

1. Pull weather for Ryan's location, current day-of-week, optionally a seed from a small bank of family phrases.
2. Prompt an LLM to design a 64x64 pixel-art Canvas theme (palette + tile sprites + animation hints), constrained by the existing Canvas JSON schema.
3. Either (a) LLM emits the JSON directly, or (b) LLM generates a 64x64 PNG and a converter rasterizes to Canvas tiles.
4. Validate against the Canvas schema. Reject + retry on bad output.
5. Upload to R2, update canvasFile URL in the device's NVS via the existing POST /set?key=canvasFile&value=... endpoint.

On-device: unchanged — Canvas already loads from canvasServer/canvasFile.

Constraints

• Canvas schema is documented but not formal — need to read the spec before letting an LLM write it.
• LLM costs: one Sonnet/Haiku call per day per device. Negligible.
• Quality control: bad themes happen. Need a fallback to yesterday's theme on validation failure, and a one-touch "redo" button.
• Aesthetic risk: variety is the feature, but a bad day's theme stares at you for 24h. Maybe vote/redo via the web UI.

Acceptance

• Pipeline produces a valid Canvas JSON given a date + weather input.
• Generated theme renders on-device without artifacts.
• Failed generation falls back gracefully (previous day's theme stays).
• Web UI exposes a "regenerate today's theme" button.
• Daily cron runs unattended for a week.

Out of scope

• Animated themes (start static; animation is a follow-up).
• Per-clock personalization (everyone on the channel gets the same theme initially).
• Accepting prompt input from the user (start fully automated).