* fix(workspaces): default new worktrees to upstream refs
Use the daemon-resolved upstream as the untouched starting ref so unpushed local commits do not leak into new workspaces. Preserve exact base identity for fork remotes while keeping local-first behavior across version drift.
* fix(workspaces): preserve exact base refs in git actions
Resolve accepted display aliases back to the stored ref before comparisons and updates. Fail closed when a non-origin remote base has no explicit mutable merge target.
* fix(workspaces): reject conflicting qualified base refs
Display aliases remain accepted for compatibility, but a qualified ref carries remote identity and must not be canonicalized to a different stored upstream.
* test(server): make upstream fixtures portable
Keep the checkout-status fixture aligned with the optional upstream field, and select main explicitly when cloning a bare test remote whose default HEAD varies by platform.
* fix(workspaces): preserve exact upstream refs
Qualified remote refs now fail closed when pruned instead of switching lineage. Metadata accepts Git-valid upstream names rather than applying a narrower character whitelist.
* fix(workspaces): preserve qualified local base refs
Local tracking branches are exact upstream identities too. Keep heuristics only for legacy unqualified metadata so origin cannot replace a stored refs/heads base.
