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/phase-planning.md

@@ -4,7 +4,7 @@ title: Phase Planning
 group: Core Features
 ---
 
-**Command:** `/gsd-plan-phase [N] [--auto] [--skip-research] [--skip-verify]`
+**Command:** `/msd-plan-phase [N] [--auto] [--skip-research] [--skip-verify]`
 
 **Purpose:** Research the implementation domain and produce verified, atomic execution plans.
 
@@ -15,7 +15,7 @@ group: Core Features
 - REQ-PLAN-04: System MUST include `read_first` and `acceptance_criteria` sections in every plan
 - REQ-PLAN-05: System MUST run plan checker verification loop (up to 3 iterations) unless `--skip-verify` is set
 - REQ-PLAN-06: System MUST support `--skip-research` flag to bypass research phase
-- REQ-PLAN-07: System MUST prompt user to run `/gsd-ui-phase` if frontend phase detected and no UI-SPEC.md exists (UI safety gate)
+- REQ-PLAN-07: System MUST prompt user to run `/msd-ui-phase` if frontend phase detected and no UI-SPEC.md exists (UI safety gate)
 - REQ-PLAN-08: System MUST include Nyquist validation mapping when `workflow.nyquist_validation` is enabled
 - REQ-PLAN-09: System MUST verify all phase requirements are covered by at least one plan before planning completes (requirements coverage gate)
 - REQ-PLAN-10: System MUST support an optional `<reversibility rating="reversible|costly|one-way">` element recording how costly a decision would be to undo, and MUST insert a `checkpoint:decision` before the task implementing a `one-way` decision unless `--no-reversibility-gates` is set (`costly` is flagged without blocking; `reversible` and unrated flow normally)