Add human-focused README.md to every skill and bundle directory

Each README is written for a human audience, explaining:
- What the skill does (not what format it follows)
- What benefit the user gets from installing it
- Quick setup and usage patterns
- When to load/trigger the skill
- What scripts, references, and templates it ships

data-scientist already had a README — left unchanged.

48 READMEs added across all skill and bundle directories.

github-runner/README.md

@@ -0,0 +1,29 @@
+# Self-Hosted GitHub Actions Runners
+
+Deploy, manage, and troubleshoot self-hosted GitHub Actions runners. Covers systemd, Docker, Kubernetes (ARC), and Scale Set Client deployments.
+
+## Why Install This Skill
+
+When your agent loads this skill, it becomes a **CI/CD infrastructure engineer** who can:
+
+- **Choose the right deployment** — systemd for single machines, Docker for homelabs, ARC for Kubernetes teams
+- **Troubleshoot registration failures** — the critical ACCESS_TOKEN vs RUNNER_TOKEN distinction
+- **Design autoscaling** — ARC, Scale Set Client, ephemeral runners
+- **Harden runner security** — public repo risks, JIT tokens, runner groups
+- **Build custom runner images** — Dockerfiles with custom toolchain, Python, Ruby
+- **Solve network issues** — firewall rules, TLS, proxy configuration
+
+## What You Get
+
+| Directory | Purpose |
+|-----------|---------|
+| `SKILL.md` | Deployment spectrum, quick reference, label strategy |
+| `references/` | 7 reference files: deployment, management, scaling, security, custom images, network, monitoring |
+
+## Triggers
+
+Load this when setting up CI, troubleshooting runner registration failures, designing autoscaling, or hardening runner security.
+
+## Requirements
+
+Linux, macOS, or Windows target hosts. Docker for containerized runners. Kubernetes for ARC deployments.