feat: wire up all Phase 2-6 features into daemon and config

Integrate all new features into the shared infrastructure:
- Config schema: add memory, discord, slack, process, web_search schemas
- Daemon wiring: memory store init, tool registration, channel adapters
- Orchestrator: memory injection into system prompt, extraction on compaction
- Agent: add setSystemPrompt() for dynamic prompt updates
- Channel/tool index: export new adapters and tool factories
- Add @slack/bolt, discord.js, turndown, linkedom, @mozilla/readability deps
- Update state.json with Phase 3b completion (494 tests passing)

src/backends/native/agent.ts

@@ -199,6 +199,10 @@ export class NativeAgent {
     return this.currentTier;
   }
 
+  setSystemPrompt(prompt: string): void {
+    this.systemPrompt = prompt;
+  }
+
   setOnToolUse(callback: ((event: ToolUseEvent) => void) | undefined): void {
     this.onToolUse = callback;
   }