docs: update migration-scripts skill

Author: ishiko732

.agents/skills/migration-scripts/SKILL.md

@@ -1,9 +1,9 @@
 ---
 name: migration-scripts
-description: Use when writing or reviewing database/config migration scripts. Enforces that migrations are frozen snapshots with no external imports.
+description: Use when writing or reviewing database/config migration scripts or migration registries. Enforces frozen-snapshot migrations, safe registration, and lean import boundaries.
 metadata:
   author: read-frog
-  version: "1.0.0"
+  version: "1.1.0"
 ---
 
 # Migration Scripts
@@ -17,10 +17,28 @@ Migration scripts must NEVER import or reference:
 
 **Why:** The codebase evolves. A migration written today references code that may change tomorrow. When that constant changes, the migration silently breaks — it now migrates to the *new* shape, not the shape that existed when the migration was written.
 
+## Rule: Migration Registries Must Validate the Chain
+
+In this repo, config migration registries should auto-discover migration files from `src/utils/config/migration-scripts/v*-to-v*.ts` (for example via `import.meta.glob`), and the registry must:
+- Parse both `fromVersion` and `toVersion` from the filename
+- Reject invalid steps like `v001-to-v003`
+- Reject duplicate target versions
+- Reject discontinuous chains
+
+Do not silently map only the target version and assume filenames are correct.
+
+## Rule: Keep Migration Imports Off Hot Paths
+
+Do not let generic config read helpers or content-script paths import migration registries unless they really perform migration.
+
+Prefer to isolate migration-aware reads/writes into dedicated modules for import/sync/restore flows, so normal runtime paths do not bundle all migration scripts unnecessarily.
+
 ## Checklist
 
 - [ ] All values are hardcoded inline (no imports from `src/`)
 - [ ] Input and output typed as `any`
 - [ ] No calls to factory functions or helpers
 - [ ] Default values are literal objects, not references to constants
 - [ ] Migration is idempotent (safe to re-run)
+- [ ] Auto-discovered registries validate `from -> to` continuity and duplicate targets
+- [ ] Migration-aware storage logic is isolated from generic read paths