Named multi-stash manager

The repository-wide Stash Manager inventories every stash entry returned by Git without a Desktop entry-count cap and supports more than one Desktop-managed stash per branch. A new stash can have a printable name, creation timestamp, branch grouping, and either all-changes or reviewed selected-file scope.

Users can inspect files, apply while keeping, pop after a clean apply, rename Desktop metadata, create and check out a branch, delete one entry, or clear an exact reviewed subset. Batch clear is limited to 100 entries. Every mutation re-resolves the stash by full object ID so shifting stash@{n} positions do not silently target another entry.

A conflicting apply retains the stash for recovery. Branch creation validates the new ref twice and consumes the stash only through Git's successful stash branch operation. Rename remains Desktop-only because rewriting another client's metadata would destroy provenance. Git storage and the bounded metadata byte budget remain the practical limits; the old 500-entry UI cap is gone.

Stash metadata is encoded in the Git stash message with bounded components; no credential or absolute path is stored. External-client entries are covered by External stash interoperability.

Verification is in the Git stash and Stash Manager UI suites, including stale identity, conflicts, named entries, multi-entry clear, and branch recovery. The separate manager dialog adds searchable tabbed export, recovery history, language and independent English/Cantonese funny-level controls, and a direct route to the shared appearance editor.