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/git-fixture.test.cjs

@@ -5,7 +5,7 @@
  *
  * Behavioral tests for tests/helpers/git-fixture.cjs's `gitOrThrow`, driving
  * the real seam against real `git` in a temp fixture repo. Covers matrix
- * section E of .gsd/phase/chore-3143-no-unbounded-spawn-guard/50-test-matrix.md.
+ * section E of .msd/phase/chore-3143-no-unbounded-spawn-guard/50-test-matrix.md.
  *
  * E10 needs to observe the exact `timeoutMs` value `gitOrThrow` forwards to
  * the seam without any wall-clock measurement (both the documented default