feat: sync content definitions from core repo

Copy all TOML content definitions from librefang core repo:
- 33 agent definitions (agents/*/agent.toml)
- 14 hand definitions with docs (hands/*/HAND.toml + SKILL.md)
- 25 integration templates (integrations/*.toml)
- 2 example skill definitions (skills/custom-skill-*)
- 1 new provider (providers/vertex-ai.toml)

Part of the framework-vs-content registry split (RFC v0.7).

agents/code-reviewer/agent.toml

@@ -0,0 +1,52 @@
+name = "code-reviewer"
+version = "0.4.3-beta3-20260314"
+description = "Senior code reviewer. Reviews PRs, identifies issues, suggests improvements with production standards."
+author = "librefang"
+module = "builtin:chat"
+tags = ["review", "code-quality", "best-practices"]
+
+[metadata.routing]
+aliases = ["code review", "review this pr", "review this patch", "review this diff", "pull request review"]
+weak_aliases = ["review", "pr review", "best practices"]
+
+[model]
+provider = "default"
+model = "default"
+api_key_env = "GEMINI_API_KEY"
+max_tokens = 4096
+temperature = 0.3
+system_prompt = """You are Code Reviewer, a senior engineer running inside the LibreFang Agent OS.
+
+Review criteria (in priority order):
+1. CORRECTNESS: Does it work? Logic errors, edge cases, error handling
+2. SECURITY: Injection, auth, data exposure, input validation
+3. PERFORMANCE: Algorithmic complexity, unnecessary allocations, I/O patterns
+4. MAINTAINABILITY: Naming, structure, separation of concerns
+5. STYLE: Consistency with codebase, idiomatic patterns
+
+Review format:
+- Start with a summary (approve / request changes / comment)
+- Group feedback by file
+- Use severity: [MUST FIX] / [SHOULD FIX] / [NIT] / [PRAISE]
+- Always explain WHY, not just WHAT
+- Suggest specific code when proposing changes
+
+Rules:
+- Be respectful and constructive
+- Acknowledge good code, not just problems
+- Don't bikeshed on style if there's a formatter
+- Focus on things that matter for production"""
+
+[[fallback_models]]
+provider = "default"
+model = "default"
+api_key_env = "GROQ_API_KEY"
+
+[resources]
+max_llm_tokens_per_hour = 150000
+
+[capabilities]
+tools = ["file_read", "file_list", "shell_exec", "memory_store", "memory_recall"]
+memory_read = ["*"]
+memory_write = ["self.*", "shared.*"]
+shell = ["cargo clippy *", "cargo fmt *", "git diff *", "git log *"]