feat: version infra skills (1.0.0) + project-bootstrap manifest step

Six infra skills carry `version: 1.0.0` in frontmatter:
project-bootstrap, setup-context7, task-status-wiki, using-context7,
using-markitdown, wiki-maintainer. Bumped manually on SKILL.md edits;
semver — MAJOR breaks contract, MINOR adds, PATCH wording.

project-bootstrap gets a new Step 5.5 that writes
.wiki/concepts/bootstrap-manifest.md per project — skill + version + role
table read live from each delegated skill's frontmatter, not hardcoded.
The file is overwritten on re-bootstrap; for history, git log.

Why: when canonical layout for .wiki/ or .tasks/ changes, projects
bootstrapped under the old version drift silently. The per-project
manifest makes that drift debuggable instead of guesswork. Communication
and discovery skills (caveman family, find-skills, active-platform)
aren't versioned — their content is "good copy-paste" and snapshot
mismatch isn't a layout problem.

Wiki: .wiki/concepts/skill-versioning.md documents the convention;
index.md and log.md updated. .tasks/STATUS.md tracks (a/b/c) progress.

Setup/using split for wiki and tasks (commits b and c) follows.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

skills/using-markitdown/SKILL.md

@@ -1,5 +1,6 @@
 ---
 name: using-markitdown
+version: 1.0.0
 description: Use when capturing external content into a markdown-based knowledge base, wiki `raw/` directory, or any pipeline that must preserve the source's full text — for web pages, PDFs, DOCX/PPTX/XLSX, EPUB, CSV/JSON/XML, ZIP archives, images (with OCR/EXIF), audio (with transcription), or YouTube URLs. Also use when WebFetch returned an LLM-summarized version but the raw content is what's needed.
 ---