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.

scripts/changeset/cli.cjs

@@ -25,8 +25,8 @@ const { renderGithubReleaseNotes } = require('./github-release-notes.cjs');
 const {
   compareSemverCore,
   isStableTripletSemver,
-} = require('../../gsd-core/bin/lib/semver-compare.cjs');
-const { packageName, repoSlug: defaultRepoSlug } = require('../../gsd-core/bin/lib/package-identity.cjs');
+} = require('../../msd-core/bin/lib/semver-compare.cjs');
+const { packageName, repoSlug: defaultRepoSlug } = require('../../msd-core/bin/lib/package-identity.cjs');
 
 function parseArgs(argv) {
   const opts = {
@@ -324,7 +324,7 @@ function resolveChangelogPath(opts) {
  *   1  — I/O error or missing required flags.
  *
  * Fix for #3496: provides a deterministic range-aware helper so the
- * `/gsd-update` show_changes_and_confirm step no longer relies on
+ * `/msd-update` show_changes_and_confirm step no longer relies on
  * vague/manual extraction that can silently skip intermediate versions.
  */
 function cmdExtract(opts) {