fix: harden pairing flow

docs/gateway/configuration.md

@@ -195,6 +195,8 @@ Controls how WhatsApp direct chats (DMs) are handled:
 - `"open"`: allow all inbound DMs (**requires** `whatsapp.allowFrom` to include `"*"`)
 - `"disabled"`: ignore all inbound DMs
 
+Pairing codes expire after 1 hour; the bot only sends a pairing code when a new request is created.
+
 Pairing approvals:
 - `clawdbot pairing list --provider whatsapp`
 - `clawdbot pairing approve --provider whatsapp <code>`

docs/gateway/security.md

@@ -38,7 +38,7 @@ Clawdbot’s stance:
 
 All current DM-capable providers support a DM policy (`dmPolicy` or `*.dm.policy`) that gates inbound DMs **before** the message is processed:
 
-- `pairing` (default): unknown senders receive a short pairing code and the bot ignores their message until approved.
+- `pairing` (default): unknown senders receive a short pairing code and the bot ignores their message until approved. Codes expire after 1 hour; repeated DMs won’t resend a code until a new request is created.
 - `allowlist`: unknown senders are blocked (no pairing handshake).
 - `open`: allow anyone to DM (public). **Requires** the provider allowlist to include `"*"` (explicit opt-in).
 - `disabled`: ignore inbound DMs entirely.