fix(changelog): match the file's list marker and lint in context

The infinito-nexus 16.0.0 message used "-" bullets on top of a
CHANGELOG.md whose older entries used "*". The standalone lint passed,
but MD004's default "consistent" style takes the marker of the first
list in the file, so the repository's own markdown lint reported every
older list and the pre-push gate refused the push.

The message now takes the marker the target CHANGELOG.md already uses,
and step 4 also lints a copy of CHANGELOG.md with the entry inserted,
since rules like MD004 and MD024 only fire across the whole file. Both
lint runs pass --no-globs so a config with its own globs does not lint
the whole tree as well.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

skills/changelog/SKILL.md

@@ -76,8 +76,13 @@ Upgrade notes:
    default of 80 unless the repo's config changes it. Aim for 78 or less, so
    lines stay within 80 after Debian's two-space indent and RPM's two-character
    `-` prefix.
-5. **Lists use `-` only**, no nesting, with a blank line before and after
-   every list (MD004, MD032).
+5. **Lists use the marker CHANGELOG.md already uses**, no nesting, with a
+   blank line before and after every list (MD004, MD032). MD004's default
+   *consistent* style takes the marker of the first list in the file, and
+   pkgmgr puts the new entry on top, so a marker that differs from the older
+   entries turns every older list into a finding. Take the marker of the first
+   list item in the existing CHANGELOG.md; use `-` only when there is no
+   CHANGELOG.md yet, and the configured one when the repo's MD004 pins a style.
 6. **No backticks and no code blocks.** pkgmgr rewrites inline code to
    *italic* in all four targets, and a fenced block fails its fallback lint.
    Write *names*, *--flags* and *paths* in `*` italics yourself; use `*`, not
@@ -98,11 +103,19 @@ config. Reproduce that exactly:
 2. From the repository root, so its config is picked up, run:
 
    ```bash
-   markdownlint-cli2 - < <scratch-file>
+   markdownlint-cli2 --no-globs - < <scratch-file>
    ```
 
+   *--no-globs* keeps the config's own globs from linting the whole tree too.
 3. A finding on line N points at message line N - 4. Shorten that line and
    lint again; print nothing until the result is 0 errors.
+4. The standalone check cannot see rules that compare the entry with the rest
+   of the file (MD004 *consistent*, MD024 duplicate headings), but the
+   repository's own markdown lint and pre-push gate do. Copy CHANGELOG.md to a
+   scratch file, insert the wrapped heading and message below its
+   `# Changelog` line, and lint that copy the same way. A finding in the older
+   entries that the unmodified CHANGELOG.md does not produce comes from the
+   new entry; fix the message, never the older entries.
 
 Without `markdownlint-cli2`, check by hand what pkgmgr's fallback checks plus
 the length limit: no line over the limit, no trailing whitespace, no