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/features/nyquist-validation.md

@@ -11,12 +11,12 @@ group: Quality Assurance Features
 - REQ-NYQ-02: System MUST map each requirement to a specific test command
 - REQ-NYQ-03: System MUST identify Wave 0 tasks (test scaffolding needed before implementation)
 - REQ-NYQ-04: Plan checker MUST enforce Nyquist compliance as 8th verification dimension
-- REQ-NYQ-05: System MUST support retroactive validation via `/gsd-validate-phase`
+- REQ-NYQ-05: System MUST support retroactive validation via `/msd-validate-phase`
 - REQ-NYQ-06: System MUST be disableable via `workflow.nyquist_validation: false`
 
 **Produces:** `{phase}-VALIDATION.md` — Test coverage contract
 
-**Retroactive Validation (`/gsd-validate-phase [N]`):**
+**Retroactive Validation (`/msd-validate-phase [N]`):**
 - Scans implementation and maps requirements to tests
 - Identifies gaps where requirements lack automated verification
 - Spawns auditor to generate tests (max 3 attempts)