feat(changelog): add release ledger data

AGENTS.md

@@ -61,13 +61,15 @@ __tests__/            # Jest tests
 
 ## Current App Behavior
 
-- Home menu shows New Game, Saves, Settings, Policies, Credits, and Toolkit.
+- Home menu shows New Game, Saves, Settings, Policies, Change Log, Credits, and Toolkit.
 - Toolkit is shown only when the resolution setting is `browser`.
 - Toolkit is clickable only when the socket status is connected.
 - Route state persists through refreshes.
 - Settings persist resolution, autosave, mute, and master/music/ambience/speech/SFX volume.
 - Browser background music is implemented in `useBackgroundMusic.web.ts`.
+- Change Log content is sourced from `src/data/changelog.json`.
 - Credits Toolkit data is sourced from `src/data/credits.json` and synced through the socket server.
+- Toolkit placeholder datasets live under `src/data/toolkit/` as empty arrays until schemas stabilize.
 
 ## Common Tasks
 
@@ -96,6 +98,13 @@ __tests__/            # Jest tests
 4. Extend `src/socket/toolkitSocketClient.ts` and a store under `src/state/` for client state.
 5. Keep Toolkit UI read-only unless editable forms are explicitly requested.
 
+### Add or change data content
+
+1. Read `src/data/AGENTS.md` first.
+2. Keep app-imported JSON covered by a typed export and runtime validation.
+3. Keep Toolkit placeholder resources as arrays in `src/data/toolkit/` until concrete schemas are requested.
+4. Add tests for new data shape, ordering, or placeholder expectations.
+
 ### Work with assets
 
 - Images: `src/assets/images/`
@@ -136,7 +145,7 @@ npm run start
 - Socket changes: run tests plus `npm run dev:toolkit` and check `/health`
 - Commit validation: `npm run validate:commit`
 
-Husky runs `npm run validate:commit` on pre-commit.
+Husky runs `npm run version:bump-build` and then `npm run validate:commit` on pre-commit. The version bump updates package metadata and public `.env` build fields for `version-yyyymmdd-last7commit` display.
 
 ## Commit Message Format