fix(cli): push per-task branch to origin before creating PR; drop dead autoCreatePr

In PR-mode, processPullRequestMergeTask called gh pr create --head
fusion/<task-id> without ever pushing the branch to origin. PR creation
failed and the task stalled in in-review — and combined with the
recover-mergeable-review sweep bug, the stalled task got force-merged
locally instead. Push the branch via git push -u origin <branch>
immediately before createPr (skipped when an existing PR already covers
the branch).

Also remove the dead autoCreatePr setting: defined as a default in the
schema and Settings type but never read anywhere.

Related to https://github.com/Runfusion/Fusion/issues/21

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

.changeset/pr-mode-push-branch-and-cleanup.md

@@ -0,0 +1,16 @@
+---
+"@runfusion/fusion": patch
+"runfusion.ai": patch
+"@fusion/core": patch
+"@fusion/dashboard": patch
+"@fusion/desktop": patch
+"@fusion/engine": patch
+"@fusion/mobile": patch
+"@fusion/pi-claude-cli": patch
+"@fusion/plugin-sdk": patch
+---
+
+Fix PR-mode merge flow (related to [#21](https://github.com/Runfusion/Fusion/issues/21)):
+
+- **PR-mode now pushes the per-task branch to origin before creating the PR.** `processPullRequestMergeTask` previously called `gh pr create --head fusion/<task-id>` without ever publishing the branch, so the PR creation failed and the task stalled in `in-review`. The branch is now pushed via `git push -u origin <branch>` immediately before `createPr` (skipped when an existing PR already covers the branch).
+- **Removed dead `autoCreatePr` setting** from the schema and `Settings` type. It was defined as a default but never read anywhere.