feat(ops): deadman switch, model health check, issue filter

Closes #115: bin/deadman-switch.sh -- alerts Telegram when zero commits for 2+ hours
Closes #116: bin/model-health-check.sh -- validates model tags against provider APIs
Closes #117: bin/issue-filter.json + live loop patches -- excludes DO-NOT-CLOSE, EPIC, META, RETRO, INTEL, MORNING REPORT, Rockachopa-assigned issues from agent pickup

All three tested locally:
- deadman-switch correctly detected 14h gap and would alert
- model-health-check parses config.yaml and validates (skips gracefully without API key in env)
- issue filters patched into live claude-loop.sh and gemini-loop.sh

bin/issue-filter.json

@@ -0,0 +1,19 @@
+{
+  "skip_title_patterns": [
+    "[DO NOT CLOSE",
+    "[EPIC]",
+    "[META]",
+    "[GOVERNING]",
+    "[PERMANENT]",
+    "[MORNING REPORT]",
+    "[RETRO]",
+    "[INTEL]",
+    "[SHOWCASE]",
+    "[PHILOSOPHY]",
+    "Master Escalation"
+  ],
+  "skip_assignees": [
+    "Rockachopa"
+  ],
+  "comment": "Shared filter config for agent loops. Loaded by claude-loop.sh and gemini-loop.sh at issue selection time."
+}