chore: add 17 operational rules and rule index

- Create .claude/rules/ with all 17 standard rule files (01-security through 17-document-imports)
- Add Operational Rules section with Rule Index to .claude/CLAUDE.md

.claude/rules/16-sub-agents.md

@@ -0,0 +1,17 @@
+# Sub-Agents and Team Agents
+
+## Use Sub-Agents (Task tool) When
+
+- Independent research tasks can run in parallel.
+- A specialized agent type matches the work (e.g., debugger, test-engineer, frontend-developer).
+- The main context window would be polluted by excessive search results.
+
+## Use Team Agents When
+
+- The task benefits from multiple specialized perspectives.
+- Code review, security audit, or test analysis is warranted.
+
+## Use Direct Tools Instead When
+
+- Simple, directed searches — use Grep/Glob directly.
+- Single-file edits or tasks under 3 steps.