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/persistent-context-threads.md

@@ -4,9 +4,9 @@ title: Persistent Context Threads
 group: v1.27 Features
 ---
 
-**Command:** `/gsd-thread [name | description]`
+**Command:** `/msd-thread [name | description]`
 
-**Purpose:** Lightweight cross-session knowledge stores for work that spans multiple sessions but doesn't belong to any specific phase. Lighter weight than `/gsd-pause-work` — no phase state, no plan context.
+**Purpose:** Lightweight cross-session knowledge stores for work that spans multiple sessions but doesn't belong to any specific phase. Lighter weight than `/msd-pause-work` — no phase state, no plan context.
 
 **Requirements:**
 - REQ-THREAD-01: System MUST support create, list, and resume modes