Adds Discord slash commands with no bot process and no gateway connection: Discord
POSTs each interaction to a FastAPI route, and the app answers it. First command is
/grade <city>, returning today's grade for a curated city from the warm cache
(reusing homepage._grade_city, so it answers well within the 3-second deadline and
costs no upstream quota).
- backend/discord_interactions.py: Ed25519 verification (PyNaCl) over the RAW
request body — Discord probes the endpoint with bad signatures and disables it if
they aren't rejected with 401. Routes PING to PONG and application-commands to
their handler; unknown/unsupported interactions are acknowledged, not errored.
City lookup is exact-name-then-prefix over the population-sorted city set; unknown
or not-yet-warm cities get an ephemeral note.
- app.py: POST {BASE}/discord/interactions, reading request.body() (not json()) so
the bytes match the signature.
- scripts/register_discord_commands.py: one-off upsert of the command definitions
via Discord REST (app id + bot token).
- PyNaCl added to requirements; Discord public-key / app-id / bot-token documented
in the env example. Endpoint URL: https://thermograph.org/discord/interactions.
Claude-Session: https://claude.ai/code/session_013dRZmX9D3JEntfMKWMTWZ8
