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.

docs/adr/660-release-from-next-head.md

@@ -108,7 +108,7 @@ or a movable tag — as the RC surface.** Concretely:
    RC tags `v<version>-rc.N` remain — each N is unique and never moved, so they are already
    immutable and serve the GitHub prerelease.
 
-4. **RC = the `@next` dist-tag, full stop.** Testers run `npm i -g @opengsd/gsd-core@next`.
+4. **RC = the `@next` dist-tag, full stop.** Testers run `npm i -g @golem15/msd-core@next`.
    Because each `rc` run is cut from `next` HEAD, every rc.N already includes all prior fixes.
    No long-lived branch, no tag movement. `finalize` promotes the released version to `@latest`
    (`@next` remains the prerelease channel managed exclusively by the `rc` job; `finalize` does not repoint it).