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/plan-import.md

@@ -4,12 +4,12 @@ title: Plan Import
 group: v1.34.0 Features
 ---
 
-**Command:** `/gsd-import --from <filepath>`
+**Command:** `/msd-import --from <filepath>`
 
-**Purpose:** Ingest an external plan file into the GSD planning system with conflict detection against `PROJECT.md` decisions, converting it to a valid GSD PLAN.md and validating it through the plan-checker.
+**Purpose:** Ingest an external plan file into the MSD planning system with conflict detection against `PROJECT.md` decisions, converting it to a valid MSD PLAN.md and validating it through the plan-checker.
 
 **Requirements:**
 - REQ-IMPORT-01: Importer MUST detect conflicts between the external plan and existing PROJECT.md decisions
 - REQ-IMPORT-02: All detected conflicts MUST be presented to the user for resolution before writing
-- REQ-IMPORT-03: Imported plan MUST be written as a valid GSD PLAN.md format
-- REQ-IMPORT-04: Written plan MUST pass `gsd-plan-checker` validation
+- REQ-IMPORT-03: Imported plan MUST be written as a valid MSD PLAN.md format
+- REQ-IMPORT-04: Written plan MUST pass `msd-plan-checker` validation