b150d79626
Generalize the Windows-only per-client stable-id map into vdisplay/identity.rs: - DisplayIdentityMap keyed on a composable string (identity_key: fingerprint, or fingerprint+resolution under per-client-mode); LRU at 15, persisted to display-identity.json (migrated from the legacy pf-vdisplay-identity.json). - Windows manager wired to it, picking the key from the identity policy. - Foundation for KWin per-slot output naming (persistent KDE scaling) — the KWin wiring is the next Stage-3 step (needs a KWin box). - Unit-tested (stable, per-client-mode split, LRU, key composition). Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>