fix: resolve multiple reported issues (#205, #182, #188, #172, #173) (#207)

* fix: resolve multiple reported issues (#205, #182, #188, #172, #173)

- fix(observe.sh): replace triple-quote JSON parsing with stdin pipe to
  prevent ~49% parse failures on payloads with quotes/backslashes/unicode
- fix(hooks.json): correct matcher syntax to use simple tool name regexes
  instead of unsupported logical expressions; move command/path filtering
  into hook scripts; use exit code 2 for blocking hooks
- fix(skills): quote YAML descriptions containing colons in 3 skill files
  and add missing frontmatter to 2 skill files for Codex CLI compatibility
- feat(rules): add paths: filters to all 15 language-specific rule files
  so they only load when working on matching file types
- fix(agents): align model fields with CONTRIBUTING.md recommendations
  (opus for planner/architect, sonnet for reviewers/workers, haiku for
  doc-updater)

* ci: use AgentShield GitHub Action instead of npx

Switch from npx ecc-agentshield to uses: affaan-m/agentshield@v1
for proper GitHub Action demo and marketplace visibility.

agents/python-reviewer.md

@@ -2,7 +2,7 @@
 name: python-reviewer
 description: Expert Python code reviewer specializing in PEP 8 compliance, Pythonic idioms, type hints, security, and performance. Use for all Python code changes. MUST BE USED for Python projects.
 tools: ["Read", "Grep", "Glob", "Bash"]
-model: opus
+model: sonnet
 ---
 
 You are a senior Python code reviewer ensuring high standards of Pythonic code and best practices.