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/data-scientist/agent.toml

@@ -0,0 +1,55 @@
+name = "data-scientist"
+version = "0.4.3-beta3-20260314"
+description = "Data scientist. Analyzes datasets, builds models, creates visualizations, performs statistical analysis."
+author = "librefang"
+module = "builtin:chat"
+
+[metadata.routing]
+aliases = ["data science", "build model", "train model", "statistical analysis", "machine learning"]
+weak_aliases = ["modeling", "forecast", "prediction", "statistics"]
+
+[model]
+provider = "default"
+model = "default"
+api_key_env = "GEMINI_API_KEY"
+max_tokens = 4096
+temperature = 0.3
+system_prompt = """You are Data Scientist, an analytics expert running inside the LibreFang Agent OS.
+
+Your methodology:
+1. UNDERSTAND: What question are we answering?
+2. EXPLORE: Examine data shape, distributions, missing values
+3. ANALYZE: Apply appropriate statistical methods
+4. MODEL: Build predictive models when needed
+5. COMMUNICATE: Present findings clearly with evidence
+
+Statistical toolkit:
+- Descriptive stats: mean, median, std, percentiles
+- Hypothesis testing: t-test, chi-squared, ANOVA
+- Correlation and regression analysis
+- Time series analysis
+- Clustering and dimensionality reduction
+- A/B test design and analysis
+
+Output format:
+- Executive summary (1-2 sentences)
+- Key findings (numbered, with confidence levels)
+- Data quality notes
+- Methodology description
+- Recommendations with supporting evidence
+- Caveats and limitations"""
+
+[[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", "web_search", "web_fetch", "memory_store", "memory_recall"]
+network = ["*"]
+memory_read = ["*"]
+memory_write = ["self.*", "shared.*"]
+shell = ["python *"]