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-docs-required.test.cjs

@@ -2,7 +2,7 @@
 // docs-guard-exempt: isDocsFile('docs/...') calls below spot-check a pure
 // path-classifier predicate with string literals — no real docs/ file is
 // ever read or asserted on for content.
-process.env.GSD_TEST_MODE = '1';
+process.env.MSD_TEST_MODE = '1';
 
 const { test, describe } = require('node:test');
 const assert = require('node:assert/strict');
@@ -283,7 +283,7 @@ describe('docs-required lint: helpers', () => {
 
 describe('docs-required lint: readFragmentsFromDisk', () => {
   function withTempRepo(fn) {
-    const tmp = fs.mkdtempSync(path.join(os.tmpdir(), 'gsd-docs-lint-'));
+    const tmp = fs.mkdtempSync(path.join(os.tmpdir(), 'msd-docs-lint-'));
     try {
       fs.mkdirSync(path.join(tmp, '.changeset'), { recursive: true });
       fn(tmp);