feat: implement model persistence with per-session overrides

- Add session_config SQLite table for per-session settings
- Update routing to support session override → agent config → global default resolution chain
- Upgrade WebChat SessionBridge from NativeAgent to AgentOrchestrator
- Add /model, /local, /cloud commands to Telegram adapter
- Add /model command to WebChat gateway handlers
- Clear session overrides on /reset command
- Pass memoryStore and config through to SessionBridge
- Add comprehensive tests for all new functionality

Fixes model persistence bug where TUI model changes didn't affect WebChat/Telegram sessions. Now:
- TUI /model sets global default (persists across restarts, affects all new sessions)
- WebChat/Telegram /model sets session override (only that conversation, cleared on /reset)
- WebChat sessions gain AgentOrchestrator features (delegation, compaction, memory)

src/daemon/services.ts

@@ -13,6 +13,7 @@ import { SkillRegistry, SkillInstaller, loadAllSkills } from '../skills/index.js
 import { assembleSystemPrompt } from '../prompt/index.js';
 import { resolve } from 'path';
 import { homedir } from 'os';
+import type { MemoryStore } from '../memory/store.js';
 
 // ── Skills ──────────────────────────────────────────────────────
 
@@ -121,6 +122,7 @@ export interface GatewayDeps {
   pairingManager?: PairingManager;
   lifecycle: Lifecycle;
   getChannelAgents: () => Map<string, { orchestrator: AgentOrchestrator; collector: OutboundAttachmentCollector }> | null;
+  memoryStore?: MemoryStore;
 }
 
 export function createGateway(deps: GatewayDeps): GatewayServer {
@@ -144,6 +146,7 @@ export function createGateway(deps: GatewayDeps): GatewayServer {
     config,
     channelRegistry,
     pairingManager,
+    memoryStore: deps.memoryStore,
     restart: async () => {
       console.log('Restart requested via gateway');
       await lifecycle.shutdown();