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.

hands/twitter/README.md

@@ -0,0 +1,34 @@
+# Twitter Hand
+
+Autonomous Twitter/X manager -- content creation, scheduled posting, engagement, and performance tracking.
+
+## Configuration
+
+| Field | Value |
+|-------|-------|
+| Category | `communication` |
+| Agent | `twitter-hand` |
+| Routing | `twitter`, `tweet`, `x.com`, `scheduled tweet` |
+
+## Integrations
+
+- **TWITTER_BEARER_TOKEN** -- Bearer Token from the Twitter/X Developer Portal.
+
+## Settings
+
+- **Content Style** -- `professional`, `casual`, `witty`, `educational`, `provocative`, `inspirational`
+- **Post Frequency** -- `1_daily`, `3_daily`, `5_daily`, `hourly`
+- **Auto Reply** -- Reply to mentions automatically (default: off)
+- **Auto Like** -- Like relevant tweets automatically (default: off)
+- **Content Topics** -- Comma-separated topics
+- **Brand Voice** -- Description of your unique voice
+- **Thread Mode** -- Include multi-tweet threads (default: on)
+- **Content Queue Size** -- `5`, `10`, `20`, `50`
+- **Engagement Hours** -- `business_hours`, `waking_hours`, `all_day`
+- **Approval Mode** -- Queue tweets for review (default: on)
+
+## Usage
+
+```bash
+librefang hand run twitter
+```