feat(teams): the slash-command seam, and the first command through it

Phase 7 of TEAMS.md. `api.registerSlashCommands` stops throwing: a module
registers a command's DEFINITION and its HANDLER together, the bot pulls the
definitions over the internal listener and runs none of our code, and the
handler executes here — forced by the bot container having no `modules` volume,
and the right boundary anyway.

Registration validates what Discord would reject as a batch (names, description
lengths, the four option types, required-before-optional), because the bot
registers the whole set in one PUT and a single bad entry costs every command
including the bot's own. Commands are not namespaced under their owner — there
is no dot in Discord's name grammar — so collisions are first-come with the
holder named.

The dispatcher is the access boundary: `linked` has no Discord equivalent, so
the platform-side permission default can only ever be advertising. It resolves
the actor by `auth_providers.kind` rather than the id slug, treats a banned
account as unlinked, bounds a handler under the bot's own timeout, and keeps
`ok` outside the envelope so a handler cannot forge it.

Liveness is asked at both the pull and the dispatch. The registries have no
removal path, so a module an operator disables at runtime would otherwise keep
a live handler behind a command Discord still advertises.

Co-Authored-By: Claude <noreply@anthropic.com>

.gitea/workflows/pr-checks.yml

@@ -86,9 +86,13 @@ jobs:
       - name: Build client
         run: npm run build --prefix client
 
-  bot-install:
-    # No tests/build to run; a clean install still catches a broken or
-    # out-of-sync lockfile before it ships in the bot image.
+  bot-tests:
+    # The install still runs first and still catches a broken or out-of-sync
+    # lockfile before it ships in the bot image — that was this job's whole
+    # purpose until phase 7 (TEAMS.md §7.1) put real logic in the bot: it now
+    # pulls slash-command definitions from the app, merges them into the
+    # whole-set PUT, and runs the defer→dispatch→edit path. None of that is
+    # reachable from the server suite, and phases 8 and 9 add more of it.
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
@@ -99,3 +103,7 @@ jobs:
           cache-dependency-path: bot/package-lock.json
       - name: Install bot deps
         run: npm ci --prefix bot
+      - name: Run bot tests
+        # Node's built-in runner, no browser and no Discord connection — the
+        # interaction is a fake that records what was called on it.
+        run: npm test --prefix bot