docs: add README for every content directory

Each directory (agents, hands, integrations, plugins, providers,
scripts, skills) now has a README documenting its TOML format,
current contents, and contribution steps.

skills/README.md

@@ -0,0 +1,80 @@
+# Skills
+
+Reusable skill definitions for LibreFang agents. Skills are either prompt templates or code scripts that agents can invoke to perform specific tasks.
+
+## Structure
+
+```
+skills/
+├── custom-skill-prompt/
+│   └── skill.toml           # Prompt-only skill
+└── custom-skill-python/
+    ├── skill.toml            # Skill manifest
+    └── main.py               # Python implementation
+```
+
+## Skill Types
+
+### Prompt-Only
+
+No code needed -- pure prompt engineering:
+
+```toml
+[skill]
+name = "meeting-agenda"
+version = "0.1.0"
+description = "Generate a structured meeting agenda"
+tags = ["meeting", "productivity"]
+
+[runtime]
+type = "promptonly"
+
+[input]
+topic = { type = "string", description = "The meeting topic", required = true }
+duration_minutes = { type = "string", description = "Duration in minutes", required = true }
+
+[prompt]
+template = """
+Create a meeting agenda for:
+Topic: {{topic}}
+Duration: {{duration_minutes}} minutes
+"""
+```
+
+### Python
+
+Custom logic with a Python entry point:
+
+```toml
+[skill]
+name = "my-skill"
+version = "0.1.0"
+description = "Skill with custom logic"
+
+[runtime]
+type = "python"
+entry = "main.py"
+
+[input]
+data = { type = "string", description = "Input data", required = true }
+```
+
+### Other Runtimes
+
+Also supported: `node`, `shell`.
+
+## Testing Skills Locally
+
+```bash
+librefang skill test ./skills/custom-skill-prompt \
+  --input '{"topic": "Q1 planning", "duration_minutes": "30"}'
+```
+
+## Adding a New Skill
+
+1. Create `skills/<name>/skill.toml`
+2. Add implementation files if not `promptonly`
+3. Run `python scripts/validate.py`
+4. Submit a PR
+
+See [CONTRIBUTING.md](../CONTRIBUTING.md) for the full guide.