refactor: remove legacy responder + agent_ux, add Gitea integration tests

Legacy removal:
- DELETE src/brain/responder.rs (900 lines) — replaced by orchestrator
- DELETE src/agent_ux.rs (184 lines) — UX moved to transport bridges
- EXTRACT chat_blocking() to src/brain/chat.rs (standalone utility)
- sync.rs: uses ConversationRegistry directly (no responder)
- main.rs: holds ToolRegistry + Personality directly (no Responder wrapper)
- research.rs: progress updates via tracing (no AgentProgress)

Gitea integration testing:
- docker-compose: added Gitea service with healthcheck
- bootstrap-gitea.sh: creates admin, org, mirrors 6 real repos from
  src.sunbeam.pt (sol, cli, proxy, storybook, admin-ui, mistralai-client-rs)
- PAT provisioning for SDK testing without Vault
- code_index/gitea.rs: fixed directory listing (direct API calls instead
  of SDK's single-object parser), proper base64 file decoding

New integration tests:
- Gitea: list_repos, get_repo, get_file, directory listing, code indexing
- Web search: SearXNG query with result verification
- Conversation registry: lifecycle + send_message round-trip
- Evaluator: rule matching (DM, own message)
- gRPC bridge: event filtering, tool call mapping, thinking→status

docker-compose.dev.yaml

@@ -48,6 +48,27 @@ services:
     volumes:
       - ./dev/searxng-settings.yml:/etc/searxng/settings.yml:ro
 
+  gitea:
+    image: gitea/gitea:1.22
+    environment:
+      - GITEA__database__DB_TYPE=sqlite3
+      - GITEA__server__ROOT_URL=http://localhost:3000
+      - GITEA__server__HTTP_PORT=3000
+      - GITEA__service__DISABLE_REGISTRATION=false
+      - GITEA__service__REQUIRE_SIGNIN_VIEW=false
+      - GITEA__security__INSTALL_LOCK=true
+      - GITEA__api__ENABLE_SWAGGER=false
+    ports:
+      - "3000:3000"
+    volumes:
+      - gitea-data:/data
+    healthcheck:
+      test: ["CMD-SHELL", "curl -sf http://localhost:3000/api/v1/version || exit 1"]
+      interval: 10s
+      timeout: 5s
+      retries: 10
+
 volumes:
   opensearch-data:
   tuwunel-data:
+  gitea-data: