feat: agent loop harness with Claude Code plugin support

Generator-evaluator architecture with iterative context-reset for
long-running coding tasks. Ships as a Claude Code plugin — install
with /plugin and use /agent-loop:init, /agent-loop:plan, /agent-loop:run.

templates/triage-brief.md.template

@@ -0,0 +1,29 @@
+# Triage Brief
+
+Generated: <!-- insert current date and time -->
+Mode: <!-- insert mode from config.json -->
+Iterations completed: <!-- insert completed count --> of <!-- insert max iterations -->
+
+## Status
+
+Stories: <!-- insert completed count --> of <!-- insert total count --> complete
+
+| ID | Title | Status | Rejections |
+|----|-------|--------|------------|
+<!-- Populated by /loop-triage skill -->
+
+## Key Findings
+
+<!-- Consolidated from progress.md session log -->
+
+## Blockers
+
+<!-- Stories that failed repeatedly or hit retry limits -->
+
+## Recommended Next Steps
+
+<!-- What a human should do next -->
+
+## Files of Interest
+
+<!-- Key files discovered or modified, with context -->