extract-summaries.ps1: INDEX.md directory tree emits SKILL.md paths as directories; CI -Check enforces wrong output

[Yu-0312]

Summary

Unreported generator bug (no open PR). skills/INDEX.md directory tree lists files as if they were directories, and CI -Check locks the wrong output in.

Reporter note: 先徵求作者方向，我會根據意見再開 PR。

Evidence

skills/scripts/extract-summaries.ps1 (~lines 93–95):

foreach ($r in $rows) {
    [void]$sb.AppendLine(("skills/{0}/" -f ($r.Path -replace '\\', '/')))
}

$r.Path is the skill file path (e.g. api-security/SKILL.md), so generated skills/INDEX.md contains:

skills/api-security/SKILL.md/
skills/apk-reverse/SKILL.md/
...

instead of:

skills/api-security/
skills/apk-reverse/
...

CI runs extract-summaries.ps1 -Check (ci.yml), which compares INDEX.md to this same generator → always green, so the drift gate cannot catch the wrong tree.

verify-doc-links.py does not treat fenced tree text as links, so it also passes.

Impact

• Auto-generated navigation index is wrong for humans and agents.
• The “INDEX is generated, do not hand-edit” contract currently enforces incorrect output.

Proposed fix (please confirm)

1. Emit directory form, e.g. module dir from Split-Path -Parent $r.Path → skills/api-security/.
2. Regenerate skills/INDEX.md in the same PR.
3. Keep -Check semantics (CI still requires INDEX matches generator).

Questions for you:

• Should the tree list only top-level skills/*/ dirs, or also nested modules (reverse-engineering/dsl-vm-reverse/)?
• Any preference on trailing slash / Markdown code fence style?

I will open a PR only after your preference on nested modules.

Scope exclusion

• Not issue skills/reverse-engineering/dsl-vm-reverse/SKILL.md is missing YAML frontmatter — the module can never be auto-discovered #148 (dsl-vm frontmatter) — current main already has frontmatter for that module.
• Not open PRs test(coherence): fail on routes with no benchmark case #131–test(routing): add bilingual R40 case-review benchmark cases #133, fix(kali): catalog yara in tool-discovery so refresh-tool-index reports it #137, fix(bootstrap): binwalk winget id does not exist, mark it manual #140–feat(docker): all-in-one Docker environment #147.