feat(grpc): dev mode, agent prefix, system prompt, error UX

- gRPC dev_mode config: disables JWT auth, uses fixed dev identity
- Agent prefix (agents.agent_prefix): dev agents use "dev-sol-orchestrator"
  to avoid colliding with production on shared Mistral accounts
- Coding sessions use instructions (system prompt + coding addendum)
  with mistral-medium-latest for personality adherence
- Conversations API: don't send both model + agent_id (422 fix)
- GrpcState carries system_prompt + orchestrator_agent_id
- Session.end() keeps session active for reuse (not "ended")
- User messages posted as m.notice, assistant as m.text (role detection)
- History loaded from Matrix room on session resume
- Docker Compose local dev stack: OpenSearch 3 + Tuwunel + SearXNG
- Dev config: localhost URLs, dev_mode, opensearch-init.sh for ML setup

dev/sol-dev.toml

@@ -0,0 +1,54 @@
+[matrix]
+homeserver_url = "http://localhost:8008"
+user_id = "@sol:sunbeam.local"
+state_store_path = "data/matrix-state"
+db_path = "data/sol.db"
+
+[opensearch]
+url = "http://localhost:9200"
+index = "sol_archive"
+memory_index = "sol_user_memory"
+batch_size = 50
+flush_interval_ms = 2000
+embedding_pipeline = "tuwunel_embedding_pipeline"
+
+[mistral]
+default_model = "mistral-medium-latest"
+evaluation_model = "ministral-3b-latest"
+research_model = "mistral-large-latest"
+max_tool_iterations = 250
+
+[behavior]
+response_delay_min_ms = 0
+response_delay_max_ms = 0
+spontaneous_delay_min_ms = 0
+spontaneous_delay_max_ms = 0
+spontaneous_threshold = 0.85
+room_context_window = 200
+dm_context_window = 200
+instant_responses = true
+memory_extraction_enabled = false
+script_fetch_allowlist = ["api.open-meteo.com", "wttr.in"]
+
+[agents]
+orchestrator_model = "mistral-medium-latest"
+compaction_threshold = 118000
+use_conversations_api = true
+coding_model = "mistral-medium-latest"
+agent_prefix = "dev"
+research_model = "ministral-3b-latest"
+research_max_iterations = 10
+research_max_agents = 25
+research_max_depth = 4
+
+[grpc]
+listen_addr = "0.0.0.0:50051"
+dev_mode = true
+
+[vault]
+url = "http://localhost:8200"
+role = "sol-agent"
+mount = "secret"
+
+[services.searxng]
+url = "http://localhost:8888"