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.

scripts/require-issue-link-policy.cjs

@@ -58,7 +58,7 @@ const EXEMPT_PATH_PREFIXES = ['tests/', 'docs/'];
 // Root-level markdown is documentation — this mirrors the repo's own doc-only
 // classifier (.claude/hooks/pre-pr-gate.sh:111), whose `[^/]+\.md` anchor is
 // deliberately root-only so runtime-loaded text under a subdirectory
-// (gsd-core/workflows/*.md, agents/*.md, commands/**/*.md) stays gated.
+// (msd-core/workflows/*.md, agents/*.md, commands/**/*.md) stays gated.
 // CHANGELOG.md is excluded: scripts/changeset/lint.cjs classes a direct edit to
 // it as user-facing precisely to close a bypass, so it must not ride in on the
 // docs carve-out either.