docs: add README for every subdirectory

33 agent READMEs, 14 hand READMEs, 2 plugin READMEs
(echo-memory + hooks), and 2 skill READMEs
(custom-skill-prompt + custom-skill-python).

Each README documents the component's purpose, configuration,
and usage based on its TOML definition.

agents/architect/README.md

@@ -0,0 +1,23 @@
+# Architect
+
+System architect. Designs software architectures, evaluates trade-offs, creates technical specifications.
+
+## Configuration
+
+| Field | Value |
+|-------|-------|
+| Module | `builtin:chat` |
+| Model | `default` |
+| Provider | `default` |
+
+System prompt instructs principled system design: separation of concerns, performance-aware design, simplicity, and explicit trade-off evaluation.
+
+## Skills
+
+- `file_read`, `file_list`, `memory_store`, `memory_recall`, `agent_send`
+
+## Usage
+
+```bash
+librefang agent run architect
+```