Task: 2. Create client_update_scale(Client *c) function
Date: 2026-07-06
Status: COMPLETED

Changes:
- include/client.h:133 — declaration added
- src/client.c:418-442 — implementation with current_outputs max scale iteration
  - Guards: null client, unmapped surface → return
  - Iterates current_outputs for max scale across visible outputs
  - Fallback to c->mon->wlr_output->scale or 1.0f
  - Safety guard: scale <= 0.0f → return
  - fabsf tolerance check before notify
  - Calls both wlr_fractional_scale_v1_notify_scale + wlr_surface_set_preferred_buffer_scale(ceilf)
- src/peachwm.c:995 — c->current_scale initialized after client_set_scale() in commitnotify()

Verification: make debug — compiles cleanly, zero warnings