Add IR communication channel integrity gates

[yZangEren]

Closes #1680.

Scope

• Adds v1.0.2 communication channel integrity gates to skills/incident-response/ir-playbook/SKILL.md.
• Requires SEV-1/SEV-2 responders to capture:
  • trust status for email, chat, ticketing, paging, phone bridges, IR-retainer portals, and endpoint-management channels;
  • the trigger and timestamp for switching to out-of-band communications;
  • participant verification and war-room/bridge access control;
  • adversary-monitoring checks for mailboxes, chat exports, IdP sessions, tickets, audit logs, and endpoint-management access;
  • decision, approval, containment order, and notification preservation evidence;
  • named approver evidence for high-impact actions;
  • return-to-normal criteria before resuming internal channels.
• Adds a Communication Channel Integrity output table.
• Adds a common-pitfall note for switching channels without preserving authority.

Validation

• git diff --check
• Markdown fence-balance check: 14 fences, balanced
• ASCII check: 0 non-ASCII characters
• Required marker checks for IR-COMMS-01, Communication Channel Integrity, return-to-normal, and v1.0.2

Payment details can be provided privately after maintainer acceptance.