feat(addons): wire the Discord add-on into packaging, catalog and docs

List the add-on in the package workflow matrix, the package checks, the host
operation policy, the catalog template and index, the case inventories of the
contract and packaging suites, and the architecture guard (two links to the
project community server are not the add-on). Document the connector in the
chats guide.

Assisted-by: Claude:claude-sonnet-5-5 go

.github/workflows/addons-package.yml

@@ -2,7 +2,7 @@
 name: 'add-on packages'
 
 # Builds, checks, signs and publishes the first-party add-on OCI packages
-# (Tables, Voice, Face, Fine-tuning, Quantization, Studio, Talk, Telegram, Slack, Office and
+# (Tables, Voice, Face, Fine-tuning, Quantization, Studio, Talk, Telegram, Slack, Discord, Office and
 # Sandbox). This workflow is
 # independent of the backend image workflows: it has its own registry input,
 # its own signer identity and its own jobs.
@@ -117,7 +117,7 @@ jobs:
     strategy:
       fail-fast: true
       matrix:
-        addon: [tables, voice, face, fine-tuning, quantization, studio, talk, telegram, slack, github, jellyfin, office, sandbox, web, memory]
+        addon: [tables, voice, face, fine-tuning, quantization, studio, talk, telegram, slack, discord, github, jellyfin, office, sandbox, web, memory]
     steps:
       - uses: actions/checkout@v7
         with:
@@ -236,7 +236,7 @@ jobs:
           # event it fails the plan. A missing or malformed platform file, or
           # any other error, fails the plan on every event.
           include='[]'
-          for id in tables voice face fine-tuning quantization studio talk telegram slack github jellyfin office sandbox web memory; do
+          for id in tables voice face fine-tuning quantization studio talk telegram slack discord github jellyfin office sandbox web memory; do
             cfg="addons/$id/package/platforms.yaml"
             err="matrix-$id.err"
             if rows=$(go run ./scripts/addons/cmd/addonpkg matrix --config "$cfg" 2>"$err"); then