docs(documentation): add page navigation and markdown rendering rules (v3.29.3)

[cheneeheng]

What

Adds Phase 4 — Page furniture and markdown that renders to
ceh-documentation:user-operator-guide, and releases it as v3.29.3.

• A breadcrumb under the H1 and a prev/next footer at the bottom of every subfolder page.
• The H1 repeats the file's ID (# HT-02 — Reset a password), so a printed or pasted page still
  says where it came from.
• index.md is the hub: no footer, lists every page grouped by subfolder in NN order.
• Markdown line-break rules — the single-newline trap, blank lines around every block element,
  3-space continuation indent inside numbered steps, no fixed-column hard wrapping.

Why

v3.29.2 gave every page a filename and nothing else. A reader landing on
how-to/HT-02-export-data.md from a search or a pasted path had no way back to the index and no way
on to HT-03 — the numbering that encodes reading order was visible only to whoever listed the
directory.

The second half exists because a guide that is correct in source and broken in a renderer is broken.
A single newline collapsing two lines into one paragraph is the most common way that happens.

How

Both halves are salvaged from docs/guide-file-naming-and-nav (90ed1b7, 2026-07-31) — a branch
that solved the v3.29.2 naming problem differently (prefix by audience, HT/OP only, numbering
global per prefix across the tree) and was superseded. Its page-furniture content was orthogonal to
that disagreement, so it was rebased onto the released scheme rather than merged:

• Chains run per subfolder, not per audience prefix, so prev/next point at siblings and need no
  ../. Only the breadcrumb climbs.
• Root-level pages are unnumbered under the released scheme, so they join no chain and take the
  breadcrumb alone. The branch numbered them (HT-01-getting-started.md, HT-90-troubleshooting.md).
• Kept verbatim in substance: the H1-repeats-ID rule, the line-break table, the blank-line rules, and
  the bulleted When/Prerequisites/Time template — that last one is the branch's own "stacked bold
  labels are a bullet list" rule applied to itself.

A dry-run merge of that branch conflicts in SKILL.md and DECISION_LOG.md and re-bumps to 1.1.5, a
version main already occupies. It carries nothing unsalvaged now and can be deleted.

Phases renumbered (write-each-procedure 4 → 5, self-review 5 → 6); the single internal phase
cross-reference in Output updated to "Phases 3-4".

Testing

• python tools/validate-plugins/validate.py → OK: all plugin checks passed
• python ceh-documentation/scripts/check-semver.py CHANGELOG.md → OK: All version entries are valid semver
• Phase headings verified sequential 1-6 with no stale cross-references.

Docs-only change; no runtime code paths touched.

Checklist

• ceh-documentation/README.md updated; root README needs no change (its row describes triggers)
• CROSS_REFERENCES.md checked — no existing skill states Markdown rendering rules, nothing to register
• Version bumped in plugin.json and marketplace.json in the same commit as the content
• DECISION_LOG.md entry 75 records the rebase and the branch's fate
• Validator green

Known consequence

Guides already generated under v3.29.2 have no footers. The skill tells the agent to edit existing
docs in place rather than relocate them, so nothing auto-migrates.

Generated with Claude Code by CEH