feat: implement tier 1 quick wins (tool groups, typing, pruning, verbose, think)

Five additive features with no breaking changes:

- Tool groups: group:fs, group:runtime, group:web, group:memory syntactic
  sugar for allow/deny lists in tool policy config
- Typing indicators: Discord sendTyping() and WhatsApp sendStateTyping()
  on message receipt for better UX feedback
- Session pruning: TTL-based auto-cleanup via sessions.ttl config with
  hourly daemon timer and SQLite GROUP BY pruning
- /verbose command: TUI command parser toggle for raw streaming display
- !!think prefix: per-message extended thinking mode wired through
  Anthropic (budget_tokens), OpenAI/GitHub (reasoning_effort), and
  Gemini (thinkingConfig) providers

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/models/gemini.ts

@@ -25,13 +25,20 @@ export class GeminiClient implements ModelClient {
       ? [{ functionDeclarations: request.tools.map(t => convertToolDefinition(t)) }]
       : undefined;
 
+    const generationConfig: Record<string, unknown> = {
+      maxOutputTokens: request.maxTokens ?? this.defaultMaxTokens,
+    };
+
+    // Extended thinking mode
+    if (request.thinking) {
+      generationConfig.thinkingConfig = { thinkingBudget: 4096 };
+    }
+
     return this.genAI.getGenerativeModel({
       model: this.model,
       systemInstruction: request.system || undefined,
       tools,
-      generationConfig: {
-        maxOutputTokens: request.maxTokens ?? this.defaultMaxTokens,
-      },
+      generationConfig,
     });
   }