chore: improve agent readiness — AGENTS.md, dependabot, CODEOWNERS, labels

- Add AGENTS.md with build commands, project structure, conventions
- Add .github/dependabot.yml for automated pip + actions updates
- Add .github/CODEOWNERS for review routing
- Expand .gitignore (.env, .DS_Store, IDE configs, coverage, venvs)
- Add C901 complexity rule to ruff (max-complexity=25, benchmarks excluded)
- Add --durations=10 to pytest CI for test performance tracking
- Add docs/schema.sql for knowledge graph schema documentation
- Created P0-P3 priority + area/* + security/performance/docs labels

.github/dependabot.yml

@@ -0,0 +1,12 @@
+version: 2
+updates:
+  - package-ecosystem: "pip"
+    directory: "/"
+    schedule:
+      interval: "weekly"
+    open-pull-requests-limit: 5
+  - package-ecosystem: "github-actions"
+    directory: "/"
+    schedule:
+      interval: "weekly"
+    open-pull-requests-limit: 3