Switch from squash merges to regular merge commits

Squash merges caused orphaned commits when pushing after auto-merge.
Regular merges preserve full commit history and avoid this issue.

- Disabled squash and rebase merge on repo settings
- Updated automerge action: MERGE_METHOD squash → merge
- Updated CLAUDE.md workflow docs

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

.github/workflows/automerge.yml

@@ -24,6 +24,6 @@ jobs:
         env:
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
           MERGE_LABELS: "automerge"
-          MERGE_METHOD: "squash"
+          MERGE_METHOD: "merge"
           MERGE_DELETE_BRANCH: "true"
           UPDATE_METHOD: "rebase"

CLAUDE.md

@@ -114,8 +114,7 @@ pnpm db:studio        # Open Drizzle Studio (DB browser)
   ```bash
   gh pr create --title "..." --body "..." --label automerge
   ```
-- PRs with `automerge` label squash-merge and delete the branch automatically
-- Use squash merges to keep main history clean
+- PRs with `automerge` label merge and delete the branch automatically
 
 ### Stacking PRs (for fast local iteration)
 When working on sequential tasks, stack branches locally: