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/helpers/exit-code-artifact-flags.cjs

@@ -9,7 +9,7 @@
  * Any call that supplies `--out` without also supplying matching overrides
  * for the other four would, under `--write`, clobber the real committed
  * `scripts/lib/exit-code-registry.cjs`, `hooks/lib/exit-code-registry.js`,
- * `src/exit-code-registry.d.cts`, and `gsd-core/bin/shared/exit-codes.sh` —
+ * `src/exit-code-registry.d.cts`, and `msd-core/bin/shared/exit-codes.sh` —
  * dangerous since test files in this repo run in parallel.
  *
  * `ensureScriptsOut` derives co-located, per-call-unique secondary/hooks/