ci: read Bun version from package.json

.github/actions/prepare/action.yml

@@ -6,7 +6,7 @@ runs:
   steps:
     - uses: oven-sh/setup-bun@v2
       with:
-        bun-version-file: .bun-version
+        bun-version-file: package.json
 
     - name: Turbo Cache
       uses: actions/cache@v5

AGENTS.md

@@ -53,9 +53,9 @@ Releases are automated and driven by Conventional Commits:
 
 ## Bun version
 
-The Bun version is pinned in `.bun-version` — the version the repo develops and builds against. Keep `packageManager` in the root `package.json` in sync with it.
+The Bun version is pinned in the root `package.json`'s `packageManager` — the version the repo develops and builds against. CI reads this pin directly from `package.json`.
 
-`engines.bun` in `packages/bun-sqlgen/pkg/package.json` is a separate decision: it's the oldest Bun the published package still runs on, not the version we build with. Raise it only when the package actually depends on a newer runtime — bumping it in lockstep with `.bun-version` drops users who could otherwise install fine.
+`engines.bun` in `packages/bun-sqlgen/pkg/package.json` is a separate decision: it's the oldest Bun the published package still runs on, not the version we build with. Raise it only when the package actually depends on a newer runtime — bumping it in lockstep with `packageManager` drops users who could otherwise install fine.
 
 ## Pull requests