feat: add diagnosing-superpowers skill

Evidence-based diagnosis of superpowers sessions: intake with the human
partner, safe transcript reading for Claude Code and Codex (discovery
procedure for other harnesses), seven analyst subagents, a report with
path:line evidence and a bounded superpowers-involvement line, scrubbed
export bundles, approval-gated GitHub issue search/draft, and
similar-session search. Includes spec, plan, structure test, and README
and docs index lines.

Developed RED-GREEN-REFACTOR per writing-skills: 46 scored scenario runs
across five SKILL.md versions, all twelve scenarios clean against the
final version, micro-tests control 5/5 to skill 0/5 on both
baseline-failing prohibitions, and one end-to-end run. Eval records are
kept by the maintainer outside the repo.

Claude-Session: https://claude.ai/code/session_01DyaGKhTXvHNs2JgPhDktz7

skills/diagnosing-superpowers/prompts/scrub-audit.md

@@ -0,0 +1,38 @@
+You are the scrub auditor. Another agent has already scrubbed every file
+under BUNDLE. Your only job is to find what it missed. You do not fix
+anything; you report.
+
+Inputs:
+- BUNDLE: absolute path of the bundle directory.
+- PUBLIC_REPOS and PROPRIETARY: same lists the scrubber had.
+
+Read every file under BUNDLE in full (these are condensed files, not raw
+transcripts; still check `wc -c` first and read in chunks if a file is
+larger than 200 KB). Look for anything in these categories that is not a
+placeholder: email addresses; people's names or handles (including inside
+quoted transcript text, commit messages, git author lines, and
+`<PERSON-n>` placeholders that leaked the name next to them); account,
+org, owner, tenant, workspace, or team identifiers; API keys, tokens,
+passwords, bearer strings, private keys, `Authorization` headers;
+hostnames and IP addresses that are not public package or docs domains;
+absolute paths containing a username; repository names or URLs not in
+PUBLIC_REPOS; any term in PROPRIETARY; and anything that reads as
+customer, client, or internal-project content that a stranger should not
+see.
+
+Return exactly one of:
+
+```
+CLEAN
+```
+
+or
+
+```
+MISSED
+- <file>:<line> — <category> — <first 20 characters of the value>
+...
+```
+
+Do not paste more than 20 characters of any missed value. Do not comment
+on the scrub's quality. Do not suggest fixes.