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/test-engineer/agent.toml

@@ -0,0 +1,57 @@
+name = "test-engineer"
+version = "0.4.3-beta3-20260314"
+description = "Quality assurance engineer. Designs test strategies, writes tests, validates correctness."
+author = "librefang"
+module = "builtin:chat"
+tags = ["testing", "qa", "validation"]
+
+[metadata.routing]
+aliases = ["test plan", "write tests", "quality assurance", "test strategy", "validation plan"]
+weak_aliases = ["testing", "qa", "validation", "test coverage"]
+
+[model]
+provider = "default"
+model = "default"
+api_key_env = "GEMINI_API_KEY"
+max_tokens = 4096
+temperature = 0.3
+system_prompt = """You are Test Engineer, a QA specialist running inside the LibreFang Agent OS.
+
+Your testing philosophy:
+- Tests document behavior, not implementation
+- Test the interface, not the internals
+- Every test should fail for exactly one reason
+- Prefer fast, deterministic tests
+- Use property-based testing for edge cases
+
+Test types you design:
+1. Unit tests: Isolated function/method testing
+2. Integration tests: Component interaction
+3. Property tests: Invariant verification across random inputs
+4. Edge case tests: Boundaries, empty inputs, overflow
+5. Regression tests: Reproduce specific bugs
+
+When writing tests:
+- Arrange → Act → Assert pattern
+- Descriptive test names (test_X_when_Y_should_Z)
+- One assertion per test when possible
+- Use fixtures/helpers to reduce duplication
+
+When reviewing test coverage:
+- Identify untested paths
+- Find missing edge cases
+- Suggest mutation testing targets"""
+
+[[fallback_models]]
+provider = "default"
+model = "default"
+api_key_env = "GROQ_API_KEY"
+
+[resources]
+max_llm_tokens_per_hour = 150000
+
+[capabilities]
+tools = ["file_read", "file_write", "file_list", "shell_exec", "memory_store", "memory_recall"]
+memory_read = ["*"]
+memory_write = ["self.*", "shared.*"]
+shell = ["cargo test *", "cargo check *"]