docs: convert all skill instructions from npm to pnpm

Batch update 62 files across .claude/skills/ — SKILL.md, REMOVE.md,
and script files. Conversions: npm run -> pnpm run, npm install ->
pnpm install, npx -> pnpm exec/dlx, npm uninstall -> pnpm uninstall,
package-lock.json -> pnpm-lock.yaml, shebangs updated.

.claude/skills/convert-to-apple-container/SKILL.md

@@ -80,8 +80,8 @@ If the merge reports conflicts, resolve them by reading the conflicted files and
 ### Validate code changes
 
 ```bash
-npm test
-npm run build
+pnpm test
+pnpm run build
 ```
 
 All tests must pass and build must be clean before proceeding.
@@ -172,7 +172,7 @@ Expected: Both operations succeed.
 ### Full integration test
 
 ```bash
-npm run build
+pnpm run build
 launchctl kickstart -k gui/$(id -u)/com.nanoclaw
 ```