Use rule-name aliases in markdownlint config

Reference rules by their readable names (line-length, no-emphasis-as-heading,
table-column-style, no-duplicate-heading) instead of MD0xx IDs.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: sir-sigurd

.markdownlint-cli2.yaml

@@ -2,15 +2,15 @@
 # for the full rule reference.
 config:
   # Line length: prose, tables, and long links routinely exceed any fixed width.
-  MD013: false
+  line-length: false
   # Bold-as-heading: the docs deliberately use bold text as inline labels.
-  MD036: false
+  no-emphasis-as-heading: false
   # Table pipe spacing: cosmetic; tables render correctly either way.
-  MD060: false
+  table-column-style: false
   # Duplicate headings: the CHANGELOG repeats Added/Changed/Fixed per release,
   # which is the Keep a Changelog convention. Only flag duplicates under the
   # same parent heading.
-  MD024:
+  no-duplicate-heading:
     siblings_only: true
 # Lint top-level docs only; spec/ holds working notes and is intentionally
 # excluded. A non-recursive glob naturally skips spec/ and .github/. This