scope diagnostics to setup and update-nanoclaw only

Remove diagnostics appendage from all other skills. Only /setup and
/update-nanoclaw need telemetry — these are the two points where we
can detect regressions and track improvements across the user base.

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

.claude/skills/x-integration/SKILL.md

@@ -414,8 +414,4 @@ docker run nanoclaw-agent ls -la /app/src/skills/
 - `data/x-browser-profile/` - Contains X session cookies (in `.gitignore`)
 - `data/x-auth.json` - Auth state marker (in `.gitignore`)
 - Only main group can use X tools (enforced in `agent.ts` and `host.ts`)
-- Scripts run as subprocesses with limited environment
-
-## Diagnostics (Optional)
-
-After completing all steps above, read and follow `.claude/skills/_shared/diagnostics.md`.
+- Scripts run as subprocesses with limited environment