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>

CHANGELOG.md

@@ -8,6 +8,7 @@
 - Agents: add Current Date & Time system prompt section with configurable time format (auto/12/24).
 - Tools: normalize Slack/Discord message timestamps with `timestampMs`/`timestampUtc` while keeping raw provider fields.
 - Docs: add Date & Time guide and update prompt/timezone configuration docs.
+- Messages: debounce rapid inbound messages across channels with per-connector overrides. (#971) — thanks @juanpablodlc.
 - Fix: guard model fallback against undefined provider/model values. (#954) — thanks @roshanasingh4.
 - Memory: make `node-llama-cpp` an optional dependency (avoid Node 25 install failures) and improve local-embeddings fallback/errors.
 - Browser: add `snapshot refs=aria` (Playwright aria-ref ids) for self-resolving refs across `snapshot` → `act`.