feat(server): inference state-graph + supervisor, memory tools, MCP client, schema, routes

- Add state-graph.ts: typed state machine for inference lifecycle
- Add supervisor.ts: agent supervisor pattern for multi-agent coordination
- Add export-formatter.ts: structured export formatting
- Add manage_memory.ts: memory CRUD tool for agent persistence
- Add get_wiki_article.ts: codecontext wiki article retrieval
- Extend memory/index.ts: 3-tier memory (context/daily/core)
- Extend MCP client: mcp-config.ts env-var substitution
- Update schema.sql: agent_sessions, tasks, pending_changes extensions
- Update API types: MessageMetadata, ErrorReason, AgentSessionConfig
- Update routes: chats, messages, sessions — column renames and agent_session_id
- Update inference: error handler, payload builder, stream phase, turn orchestrator

apps/server/src/schema.sql

@@ -234,6 +234,7 @@ ALTER TABLE sessions ADD COLUMN IF NOT EXISTS workspace_panes JSONB NOT NULL DEF
 ALTER TABLE sessions ADD COLUMN IF NOT EXISTS status TEXT NOT NULL DEFAULT 'open';
 
 -- v1.2: chats table
+-- per-chat-model-switching v2.x: ALTER below adds the model override column.
 CREATE TABLE IF NOT EXISTS chats (
   id           UUID PRIMARY KEY DEFAULT gen_random_uuid(),
   session_id   UUID NOT NULL REFERENCES sessions(id) ON DELETE CASCADE,
@@ -244,6 +245,9 @@ CREATE TABLE IF NOT EXISTS chats (
 );
 CREATE INDEX IF NOT EXISTS idx_chats_session_status ON chats (session_id, status, updated_at DESC);
 
+-- v2.7.x: per-chat model override. NULL = inherit from session.model.
+ALTER TABLE chats ADD COLUMN IF NOT EXISTS model TEXT;
+
 -- v1.2: messages.chat_id + messages.kind
 ALTER TABLE messages ADD COLUMN IF NOT EXISTS chat_id UUID REFERENCES chats(id) ON DELETE CASCADE;
 ALTER TABLE messages ADD COLUMN IF NOT EXISTS kind TEXT NOT NULL DEFAULT 'message';
@@ -320,6 +324,9 @@ BEGIN
   END IF;
 END $$;
 
+-- per-chat-model-switching: per-chat model override. NULL = inherit from session model.
+ALTER TABLE chats ADD COLUMN IF NOT EXISTS model TEXT;
+
 -- v1.x-batch9: per-session agent reference. Agent definitions are not stored in
 -- the DB; they live in builtins (services/agents.ts) and a per-project AGENTS.md.
 -- agent_id is the slugified agent name. NULL means "use BooCode defaults".
@@ -355,6 +362,11 @@ INSERT INTO settings (key, value) VALUES ('theme_mode', '"dark"') ON CONFLICT (k
 ALTER TABLE projects ADD COLUMN IF NOT EXISTS default_system_prompt TEXT NOT NULL DEFAULT '';
 ALTER TABLE projects ADD COLUMN IF NOT EXISTS default_web_search_enabled BOOLEAN NOT NULL DEFAULT false;
 ALTER TABLE sessions ADD COLUMN IF NOT EXISTS web_search_enabled BOOLEAN;
+
+-- v[state-graph]: optional declarative state-graph engine flag. Default OFF
+-- (existing procedural while loop). When ON, runAssistantTurn routes
+-- through runGraph in state-graph.ts for node-based execution.
+ALTER TABLE sessions ADD COLUMN IF NOT EXISTS state_graph_enabled BOOLEAN NOT NULL DEFAULT FALSE;
 ALTER TABLE sessions DROP COLUMN IF EXISTS tags;
 
 -- v1.11: anchored rolling compaction.