Add "Using scripts" guide for skill creators (#196)

* Add "Using scripts" guide for skill creators

New guide at `docs/skill-creation/using-scripts.mdx` covering how to use
commands and scripts in skills:

- One-off commands with `uvx`, `pipx`, `npx`, `bunx`, `go run`,
  `deno run` (tabbed by ecosystem, with pinned version examples)
- Referencing bundled scripts from `SKILL.md` using relative paths
- Self-contained scripts with inline dependency declarations (PEP 723,
  Deno `npm:` imports, Bun auto-install, Ruby `bundler/inline` — tabbed
  with a common HTML-parsing example)
- Designing scripts for agentic use: non-interactive execution, `--help`
  documentation, error messages, structured output, and a compressed
  checklist of further considerations

Also updates `docs/docs.json` to organize navigation into groups ("For
skill creators" and "For client implementors").

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* Address review feedback on "Using scripts" guide

Relative paths note: Clarify that the convention applies to support
files like `references/*.md`, and explain *why* (the agent runs commands
from the skill root).

Structured output: Reframe motivation around composability with both
agents and standard tools (`jq`, `cut`, `awk`) rather than LLM parsing
ambiguity. Shorten prose; let the code example's inline comments carry
the contrast.

Predictable output size: Add `--output` flag as an alternative strategy
for scripts whose output is large and not amenable to pagination. The
`--output` flag acts as a consent mechanism — the agent must explicitly
choose a file destination or pass `-` to opt in to stdout, preventing
accidental context-window flooding.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

docs/docs.json

@@ -19,7 +19,18 @@
       "home",
       "what-are-skills",
       "specification",
-      "integrate-skills"
+      {
+        "group": "For skill creators",
+        "pages": [
+          "skill-creation/using-scripts"
+        ]
+      },
+      {
+        "group": "For client implementors",
+        "pages": [
+          "integrate-skills"
+        ]
+      }
     ]
   },
   "contextual": {