Add INCIDENT_RESPONSE_FRAMEWORK to domainPrompts.ts and append it to
all 17 domain prompts via getDomainPrompt(). Add system_prompt param
to chat_message command so frontend can inject domain expertise. Record
UTC timeline events (triage_started, log_uploaded, why_level_advanced,
root_cause_identified, rca_generated, postmortem_generated,
document_exported) at key moments with non-blocking calls.
Update tauriCommands.ts with getTimelineEventsCmd, optional metadata on
addTimelineEventCmd, and systemPrompt on chatMessageCmd.
12 new frontend tests (9 domain prompts, 3 timeline events).
