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/frontmatter.unit.test.cjs

@@ -3,7 +3,7 @@
 /**
  * Unit tests for frontmatter.cjs
  *
- * Module: gsd-core/bin/lib/frontmatter.cjs
+ * Module: msd-core/bin/lib/frontmatter.cjs
  *
  * Covers:
  *   - extractFrontmatter: all scalar types, quoted, arrays, nested, edge cases
@@ -30,7 +30,7 @@ const {
   agentScalarNeedsDoubleQuoting,
   escapeDoubleQuotedScalar,
   propagateCommentChannel,
-} = require('../gsd-core/bin/lib/frontmatter.cjs');
+} = require('../msd-core/bin/lib/frontmatter.cjs');
 
 // ─── extractFrontmatter ───────────────────────────────────────────────────────