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/lint-workflow-shellcheck.test.cjs

@@ -14,7 +14,7 @@
  * Note: scripts/lint-workflow-shellcheck.cjs guards its CLI entry point
  * with `if (require.main === module) runMain(main);`, so requiring it here
  * for its exported pure functions does not also trigger a live ShellCheck
- * run against the real gsd-core/workflows/ tree.
+ * run against the real msd-core/workflows/ tree.
  */
 
 const { test, describe } = require('node:test');