chore(evidence): add wave 1 scale-update research evidence

- task-2: fractional-scale-v1 research notes for client surfaces
- task-3: fractional-scale-v1 research notes for layer surfaces + transparency/blur notes

.omo/evidence/task-2-wlr-fractional-scale-manager-v1.txt

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+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

.omo/evidence/task-3-transparency-blur.md

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+## task-3-transparency-blur
+
+### Field added
+- File: include/client.h
+- Line 39: `struct wlr_scene_blur *blur;`
+- Placement: after `struct wlr_scene_shadow *shadow;` (line 38)
+
+### Context
+- Forward declaration not needed — definition provided by `<scenefx/types/wlr_scene.h>` through monitor.h include chain.
+- Field initialized to NULL by ecalloc in createnotify (peachwm.c:1245).
+- No `#include` directives added.

.omo/evidence/task-3-wlr-fractional-scale-manager-v1.txt

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+Task: 3. Create layersurface_update_scale(LayerSurface *l) function
+Date: 2026-07-06
+Status: COMPLETED
+
+Changes:
+- src/peachwm.c:912-941 — static function with current_outputs max scale iteration
+  - Guards, current_outputs iteration, fallback, safety guard, fabsf check
+  - Marked __attribute__((unused)) until wired in later task
+- src/peachwm.c:952 — l->current_scale initialized after client_set_scale() in commitlayersurfacenotify() initial-commit path
+
+Verification: make debug — compiles cleanly, zero warnings