feat(skills): add inbox-priority-agent triage skill

skills/inbox-priority-agent/references/priority-rubric.md

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+# Priority Rubric
+
+Use this rubric to map inbound items to a single priority level.
+
+## Scoring Dimensions
+
+Score each dimension 0-3, then sum.
+
+- **Urgency (0-3)**
+  - 3: Needs action now or within 2 hours
+  - 2: Needs action today
+  - 1: Needs action this week
+  - 0: No clear time pressure
+
+- **Importance (0-3)**
+  - 3: High impact on commitments, money, safety, or key relationships
+  - 2: Meaningful impact on active goals/projects
+  - 1: Useful but non-critical
+  - 0: Minimal impact
+
+- **Consequence of delay (0-3)**
+  - 3: Major downside if delayed (missed deadline, escalation)
+  - 2: Moderate downside
+  - 1: Minor downside
+  - 0: No meaningful downside
+
+## Priority Mapping
+
+- **P1 (Now):** total 7-9, or explicit hard deadline <= 2h
+- **P2 (Soon):** total 5-6, or hard deadline today
+- **P3 (Watch):** total 3-4
+- **P4 (Low):** total 0-2
+
+## Tie-Breakers
+
+If two items tie, rank higher when one has:
+1. Explicit deadline
+2. Direct ask from a high-priority stakeholder
+3. Thread with unresolved blocker
+4. Higher recency (newer unresolved item)
+
+## Draft Reply Patterns
+
+Use concise variants:
+
+- **Acknowledge + ETA**
+  - "Got this — I’ll send you an update by [time]."
+
+- **Clarify blocker**
+  - "I can do this next, but I need [missing info] first."
+
+- **Defer politely**
+  - "Noted. I can take this on [day/time] unless priorities change."
+
+- **Escalate responsibly**
+  - "This looks time-sensitive. Recommending we handle it first because [reason]."