chore(workspace): add hardened startup/security workflows and skill suite

skills/_shared/briefing-conventions.md

@@ -0,0 +1,35 @@
+# Shared Briefing Conventions
+
+Use these conventions across `daily-brief`, `calendar-sentinel`, and `inbox-triage` outputs.
+
+## Priority labels
+
+- **P1 Urgent**: immediate action needed (time-sensitive/blocker)
+- **P2 Important**: action needed soon, not immediate
+- **P3 Routine**: useful but can wait
+- **P4 FYI**: informational, no action required
+
+## Time windows
+
+- **Now**: next 2 hours
+- **Soon**: next 24 hours
+- **Watch**: beyond 24h or lower confidence risks
+
+## Standard output frame
+
+1. **Now** (P1)
+2. **Soon** (P2)
+3. **Watch** (P3/P4)
+4. **Next actions (1-3)** ordered, concrete steps
+
+## Noise controls
+
+- Prefer one batched update over many small pings.
+- Suppress unchanged low-priority repeats.
+- If no meaningful change, send a brief all-clear.
+
+## Writing style
+
+- Keep bullets short.
+- Include only action-relevant context.
+- End with clear next steps.