docs: add Claude Code marketplace install + README instructions

Adds .claude-plugin/marketplace.json so the repo can be installed as a
Claude Code plugin via:

  /plugin marketplace add jkneen/dgx-spark-playbooks
  /plugin install dgx-spark-playbooks@dgx-spark-playbooks

Documents both the marketplace path and the local git clone + install.sh
path in the README, including how to customize skills via overrides/.

.claude-plugin/marketplace.json

@@ -0,0 +1,14 @@
+{
+  "name": "dgx-spark-playbooks",
+  "owner": {
+    "name": "Jason Kneen",
+    "email": "jason@bouncingfish.com"
+  },
+  "plugins": [
+    {
+      "name": "dgx-spark-playbooks",
+      "source": "./",
+      "description": "Skills for setting up AI/ML workloads on NVIDIA DGX Spark hardware — derived from the official DGX Spark playbooks."
+    }
+  ]
+}

README.md

@@ -17,6 +17,39 @@ These playbooks provide detailed instructions for:
 
 Each playbook includes prerequisites, step-by-step instructions, troubleshooting guidance, and example code.
 
+## Use as Claude Code Skills
+
+Every playbook in this repo is also exposed as a [Claude Code](https://docs.claude.com/claude-code) skill, so Claude can install and configure them for you interactively. An index skill (`dgx-spark`) routes broad questions to the right specific playbook, and each leaf skill carries cross-references to related playbooks (prerequisites, alternatives, what to try next).
+
+### Option A: install via Claude Code plugin marketplace (recommended)
+
+In Claude Code, run:
+
+```
+/plugin marketplace add jkneen/dgx-spark-playbooks
+/plugin install dgx-spark-playbooks@dgx-spark-playbooks
+```
+
+### Option B: install locally via script
+
+Clone and run the install script. This symlinks each skill into `~/.claude/skills/`, so `git pull` updates them in place.
+
+```bash
+git clone https://github.com/jkneen/dgx-spark-playbooks
+cd dgx-spark-playbooks
+./scripts/install.sh                  # individual skills → ~/.claude/skills/
+./scripts/install.sh --plugin         # or: whole repo as a plugin → ~/.claude/plugins/
+./scripts/uninstall.sh                # remove
+```
+
+Requires Node 18+ if you want to regenerate skills from overrides; otherwise the committed `skills/` directory is used as-is.
+
+### Customizing a skill
+
+Hand-curate any skill by creating or editing `overrides/<playbook-name>.md` (see [`overrides/ollama.md`](overrides/ollama.md) as a worked example), then run `node scripts/generate.mjs` to rebuild. Overrides contribute the frontmatter `description` (which controls when the skill triggers) and any extra sections like "Related skills" or gotchas. Generated content between `<!-- GENERATED:BEGIN -->` and `<!-- GENERATED:END -->` markers is rewritten from the upstream README on every regeneration; override content outside those markers is preserved.
+
+A GitHub Action auto-regenerates `skills/` whenever a playbook README or override changes.
+
 ## Available Playbooks
 
 ### NVIDIA