feat: unify installation model catalog

docs/install/examples/thothii-installation.local.yaml

@@ -1,6 +1,7 @@
 # Copy this file to a protected operator-controlled path named exactly thothii-installation.yaml
 # and set mode 0600 (or 0400) before using it as THT_INSTALLATION_CONFIG_SOURCE.
 # Replace every absolute placeholder. Select exactly one Git transport override.
+schemaVersion: 2
 profile: local
 projectDirectory: "/absolute/path/to/ThothII"
 envFile: "/absolute/path/to/ThothII/deploy/env/local.env"
@@ -8,17 +9,27 @@ workspaceRepository:
   remote: git@git.example.com:organization/workspaces.git
   branch: main
   access: ssh
-metadataGeneration:
-  default: openai-mini
-  models:
-    - id: openai-mini
-      label: OpenAI Mini
-      litellm:
-        provider: openai
-        model: gpt-4.1-mini
-      apiKeyEnv: OPENAI_API_KEY
-    # apiKeyEnv may be omitted only for an explicit endpoint that accepts
-    # unauthenticated requests.
+modelCatalog:
+  defaults:
+    session: deepseek/deepseek-v4-pro
+    metadataGeneration: openai/gpt-4.1-mini
+  embedding:
+    id: ollama/qwen3-embedding:0.6b
+    dimensions: 1024
+  providers:
+    deepseek:
+      authentication: {mode: pi_auth}
+      session: {mode: pi_builtin}
+      models:
+        deepseek-v4-pro:
+          session: {}
+    openai:
+      authentication: {mode: secret_env, apiKeyEnv: OPENAI_API_KEY}
+      metadataGeneration: {litellmProvider: openai}
+      models:
+        gpt-4.1-mini:
+          label: OpenAI Mini
+          metadataGeneration: {}
 authentication:
   configDirectory: "/absolute/path/to/thothii-auth"
 overrides: