* fix(sync): use sync-branch worktree for --full --no-pull (#1173)
Bug 1: PullFromSyncBranch was copying uncommitted worktree changes to
main repo when remoteAhead==0. This corrupted the 3-way merge because
local changes appeared as remote changes. Fixed by copying only the
committed state from HEAD instead of the working directory.
Bug 2: doExportOnlySync was checking main repo for changes via
gitHasBeadsChanges, but when sync-branch is configured, changes go to
the worktree, not main. Fixed by detecting sync-branch config and using
CommitToSyncBranch which operates on the worktree.
Fixes#1173
* refactor(sync): consolidate sync-branch detection and commit/push logic
Extract repeated patterns into reusable helpers:
- SyncBranchContext struct: holds branch name and repo root
- getSyncBranchContext(): detects sync-branch config from store
- commitAndPushBeads(): handles both sync-branch and regular git workflows
This eliminates duplicated sync-branch detection code (was in 3 places)
and the duplicated commit/push conditional logic (was in 2 places).
Net reduction of ~20 lines while improving maintainability.
* fix: remove unused bool return from commitAndPushBeads
f336e669e9