feat(whatsapp): add debounceMs for batching rapid messages (#971)

* feat(whatsapp): add debounceMs for batching rapid messages

Add a `debounceMs` configuration option to WhatsApp channel settings
that batches rapid consecutive messages from the same sender into a
single response. This prevents triggering separate agent runs for
each message when a user sends multiple short messages in quick
succession (e.g., "Hey!", "how are you?", "I was wondering...").

Changes:
- Add `debounceMs` config to WhatsAppConfig and WhatsAppAccountConfig
- Implement message buffering in `monitorWebInbox` with:
  - Map-based buffer keyed by sender (DM) or chat ID (groups)
  - Debounce timer that resets on each new message
  - Message combination with newline separator
  - Single message optimization (no modification if only one message)
- Wire `debounceMs` through account resolution and monitor tuning
- Add UI hints and schema documentation

Usage example:
{
  "channels": {
    "whatsapp": {
      "debounceMs": 5000  // 5 second window
    }
  }
}

Default behavior: `debounceMs: 0` (disabled by default)

Verified: All existing tests pass (3204 tests), TypeScript compilation
succeeds with no errors.

Implemented with assistance from AI coding tools.

Closes #967

* chore: wip inbound debounce

* fix: debounce inbound messages across channels (#971) (thanks @juanpablodlc)

---------

Co-authored-by: Peter Steinberger <steipete@gmail.com>

src/auto-reply/reply.triggers.trigger-handling.shows-quick-model-picker-grouped-by-model.test.ts

@@ -263,9 +263,7 @@ describe("trigger handling", () => {
 
       const text = Array.isArray(res) ? res[0]?.text : res?.text;
       // Selecting the default model shows "reset to default" instead of "set to"
-      expect(normalizeTestText(text ?? "")).toContain(
-        "anthropic/claude-opus-4-5",
-      );
+      expect(normalizeTestText(text ?? "")).toContain("anthropic/claude-opus-4-5");
 
       const store = loadSessionStore(cfg.session.store);
       // When selecting the default, overrides are cleared