refactor: hard-fork GSD -> MSD (Make Software Done)

Mechanical rename produced by scripts/msd-rename.cjs: gsd/Gsd/GSD -> msd/Msd/MSD
across contents and paths, upstream package/repo coordinates -> @golem15/msd-core
and golem15com/msd-core. Deep links into upstream history, sibling upstream
packages, the GSD-2 import feature, CHANGELOG.md and .changeset/ are kept as-is.

Hand edits on top: MSD block-letter banner and logos, LICENSE copyright line,
package/plugin identity, regenerated lockfile, install-tree fixtures, derived
registries and benchmark baseline; migration checksum baseline re-locked
(MSD keeps its own install state, so no install had applied the old sums);
sort-order and regex-escaped expectations in tests adjusted.

tests/markdown-sectionizer.test.cjs

@@ -3,7 +3,7 @@
 /**
  * Behavioral tests for markdown-sectionizer.cjs
  *
- * Module: gsd-core/bin/lib/markdown-sectionizer.cjs
+ * Module: msd-core/bin/lib/markdown-sectionizer.cjs
  * Exports: stripFencedCode, stripInlineCode, extractFencedBlock, tokenizeHeadings,
  *          collectSections, collectSection, iterateBullets, updateBullet,
  *          extractTaggedBlocks, stripTaggedBlocks, replaceSection, withSection,
@@ -46,7 +46,7 @@ const {
   deleteSection,
   stripInlineCode,
   scanInlineCodeSpans,
-} = require('../gsd-core/bin/lib/markdown-sectionizer.cjs');
+} = require('../msd-core/bin/lib/markdown-sectionizer.cjs');
 
 // ─── stripInlineCode (#2365) ──────────────────────────────────────────────────