Namespace patch names by synth ({synth}/{name})

[pnilan]

Problem

Patch names are currently globally unique. Saving a patch named "bass" for tb-03 silently overwrites an existing "bass" patch for minitaur. Users should be able to have the same patch name across different synths.

Proposed Solution

Change the DB uniqueness constraint from UNIQUE(name) to UNIQUE(name, synth) and use {synth}/{name} (e.g., minitaur/bass) as the display and lookup format.

Key changes

• Schema migration: UNIQUE(name) → UNIQUE(name, synth). Use Alembic (or similar) for the DB migration so existing patches.db files are upgraded cleanly.
• patch_library.py: Update get() and delete() to accept optional synth param. Add find(name) for disambiguation. Update upsert logic to key on (name, synth).
• tools/patches.py: Add _parse_patch_ref() helper to parse "minitaur/bass" → (synth, name). Update load_patch, recall_patch, delete_patch to support both "bass" (unambiguous) and "minitaur/bass" (explicit) lookups, with clear error messages when ambiguous.
• Display: list_patches shows "minitaur/bass" format instead of "bass (Minitaur)".

Disambiguation behavior

• recall_patch("bass") — works if only one synth has a patch named "bass"
• recall_patch("minitaur/bass") — always unambiguous
• If ambiguous, return error: "Multiple patches named 'bass': minitaur/bass, tb-03/bass"

Context

Identified during review of PR #6 (Phase 3: Patch Library). Currently tracked as a known limitation.