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/post-execute-codebase-drift-detection.md

@@ -6,12 +6,12 @@ order: 27.2
 ---
 
 **Introduced by:** #2003
-**Trigger:** Runs automatically at the end of every `/gsd-execute-phase`
+**Trigger:** Runs automatically at the end of every `/msd-execute-phase`
 **Configuration:**
 - `workflow.drift_threshold` (integer, default `3`) — minimum new
   structural elements before the gate acts.
 - `workflow.drift_action` (`warn` | `auto-remap`, default `warn`) —
-  warn-only or spawn `gsd-codebase-mapper` with `--paths` scoped to
+  warn-only or spawn `msd-codebase-mapper` with `--paths` scoped to
   affected subtrees.
 
 **What counts as drift:**
@@ -30,6 +30,6 @@ continues. Drift detection cannot fail verification.
 - REQ-DRIFT-02: Action fires only when element count ≥ `workflow.drift_threshold`
 - REQ-DRIFT-03: `warn` action MUST NOT spawn any agent
 - REQ-DRIFT-04: `auto-remap` action MUST pass sanitized `--paths` to the mapper
-- REQ-DRIFT-05: Detection/remap failure MUST be non-blocking for `/gsd-execute-phase`
+- REQ-DRIFT-05: Detection/remap failure MUST be non-blocking for `/msd-execute-phase`
 - REQ-DRIFT-06: `last_mapped_commit` round-trip through YAML frontmatter
   on each `.planning/codebase/*.md` file