[#1275] Fix Release Notes and Getting Started page titles (#1276)

The Release Notes and Getting Started chapter pages currently appear as
AsciiDoc filenames in navigation and default xrefs, and their browser
titles are `Untitled`. Give all four pages proper title metadata while
retaining their existing URLs, HTML fragments and combined-book chapter
hierarchy.

Use the existing `:table-caption!:` insertion point in doc-maven-plugin
3.2.2 to promote chapter headings only in the generated Antora output.
Keep chapter IDs on headings for the books and emit separate inline
anchors under `env-site`, because the default Antora UI does not render
document IDs as HTML anchors.

Add six integration checks in the `man-pages` profile's `verify` phase,
after Antora generation. They verify the expected document titles with
header-only parsing, reject a `:title:` attribute that could mask a
missing document header, and render the page bodies to check all 16
published chapter and subsection fragment IDs. They also preserve both
combined books' chapter titles, IDs and levels. Missing generated inputs
or a missing test include fail the build.

Document the checks and source conventions in `CHECKS.md`, including the
blank line required after each inline anchor and the different effect of
a block anchor on a section's automatic ID.

Fixes #1275.

## Validation

Current revision:

- All 26 documentation-module unit tests and six integration checks
passed on Java 11 and Java 27, with no failures, errors or skips.
- On Java 11, the strengthened integration checks accept the original
generated pages and reject each of three generated-input mutations:
removing the blank line after the requirements page's inline anchor,
replacing it with a block anchor, and replacing the title-promotion
attributes with `:title:`. The first two fail on the missing published
subsection ID; the third fails on the title attribute.
- `git diff --check` passed.

Earlier validation of the page-title and anchor changes:

- Reproduced four missing-title failures before the fix and four
missing-HTML-anchor failures before preserving the body anchors.
- Built an Antora 3.1.15 preview and verified browser titles,
landing-page/default xref labels, navigation labels and all 16
previously published content fragment IDs, with no duplicate IDs.
- Rebuilt both PDFs using doc-maven-plugin 3.2.2; checked their rendered
contents pages, chapter structure and named destinations.
- The attribute checker and 600 file xrefs across 72 pages passed.

The current revision changes only the integration test and `CHECKS.md`;
the Antora preview, PDFs, attribute checker and xref scan were not rerun
for this update. Validation used focused documentation goals; the full
reactor was not rerun. Existing Maven/JRuby/JDK access and deprecation
warnings remain. The live documentation site has not been deployed by
this change.