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/config/schema.ts

@@ -168,6 +168,7 @@ const FIELD_LABELS: Record<string, string> = {
   "session.agentToAgent.maxPingPongTurns": "Agent-to-Agent Ping-Pong Turns",
   "messages.ackReaction": "Ack Reaction Emoji",
   "messages.ackReactionScope": "Ack Reaction Scope",
+  "messages.inbound.debounceMs": "Inbound Message Debounce (ms)",
   "talk.apiKey": "Talk API Key",
   "channels.whatsapp": "WhatsApp",
   "channels.telegram": "Telegram",
@@ -189,6 +190,7 @@ const FIELD_LABELS: Record<string, string> = {
   "channels.telegram.timeoutSeconds": "Telegram API Timeout (seconds)",
   "channels.whatsapp.dmPolicy": "WhatsApp DM Policy",
   "channels.whatsapp.selfChatMode": "WhatsApp Self-Phone Mode",
+  "channels.whatsapp.debounceMs": "WhatsApp Message Debounce (ms)",
   "channels.signal.dmPolicy": "Signal DM Policy",
   "channels.imessage.dmPolicy": "iMessage DM Policy",
   "channels.discord.dm.policy": "Discord DM Policy",
@@ -327,6 +329,8 @@ const FIELD_HELP: Record<string, string> = {
   "messages.ackReaction": "Emoji reaction used to acknowledge inbound messages (empty disables).",
   "messages.ackReactionScope":
     'When to send ack reactions ("group-mentions", "group-all", "direct", "all").',
+  "messages.inbound.debounceMs":
+    "Debounce window (ms) for batching rapid inbound messages from the same sender (0 to disable).",
   "channels.telegram.dmPolicy":
     'Direct message access control ("pairing" recommended). "open" requires channels.telegram.allowFrom=["*"].',
   "channels.telegram.streamMode":
@@ -348,6 +352,8 @@ const FIELD_HELP: Record<string, string> = {
   "channels.whatsapp.dmPolicy":
     'Direct message access control ("pairing" recommended). "open" requires channels.whatsapp.allowFrom=["*"].',
   "channels.whatsapp.selfChatMode": "Same-phone setup (bot uses your personal WhatsApp number).",
+  "channels.whatsapp.debounceMs":
+    "Debounce window (ms) for batching rapid consecutive messages from the same sender (0 to disable).",
   "channels.signal.dmPolicy":
     'Direct message access control ("pairing" recommended). "open" requires channels.signal.allowFrom=["*"].',
   "channels.imessage.dmPolicy":