Issue #20: Panels: resize the left sidebar and the right panel by dragging their edge

Both side panels had an exact width. They are now resizable egui panels
whose width lives in UiState (leftWidth / rightWidth, serde, sanitized on
load) so it survives panel switches, view changes and restarts; egui's
own remembered size is dropped each frame and only a drag of the edge
writes back (measured from the fixed edge to the pointer, so content
wider than the panel can't creep it). Limits: left 200–480 pt, right
250–520 pt, and the photo area keeps at least 360 pt; a narrower window
shrinks the panels without forgetting the chosen width. The bottom bar,
which sits between the panels, now drops Copy/Paste Edit Settings and
then the rating pill when its centre has no room instead of overlapping
the zoom controls. The unused left_w theme token is gone.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

docs/parity.md

@@ -44,13 +44,13 @@ and prints the summary; `cargo xtask parity --write` refreshes the summary table
 | U. Map & location (MAP) | 0 | 1 | 1 | 0 | — | 0/1 (0%) |
 | V. Preferences (PREF) | 5 | 0 | 3 | 3 | 1/1 (100%) | 4/4 (100%) |
 | W. Cloud & AI infrastructure (CLOUD / AI) | 1 | 0 | 1 | 2 | — | — |
-| X. Cross-cutting behaviours (BEHAV) | 14 | 1 | 2 | 1 | 8/8 (100%) | 5/5 (100%) |
+| X. Cross-cutting behaviours (BEHAV) | 15 | 1 | 2 | 1 | 8/8 (100%) | 6/6 (100%) |
 | Y. Menus | 81 | 0 | 4 | 8 | 47/47 (100%) | 23/23 (100%) |
 | Z. Keyboard shortcuts (desktop) | 74 | 3 | 3 | 1 | 49/52 (94%) | 22/23 (96%) |
 | Lightroom Classic extras | 29 | 9 | 41 | 9 | — | 20/21 (95%) |
-| **Total** | 383 | 25 | 92 | 37 | 194/198 (98%) | 136/144 (94%) |
+| **Total** | 384 | 25 | 92 | 37 | 194/198 (98%) | 137/145 (94%) |
 
-Weighted completion (✅ = 1, 🟡 = ½, 🚫 left out): **79.1%** of 500 in-scope rows — P0 99.0% of 198 · P1 96.2% of 144 · P2 38.6% of 158.
+Weighted completion (✅ = 1, 🟡 = ½, 🚫 left out): **79.1%** of 501 in-scope rows — P0 99.0% of 198 · P1 96.2% of 145 · P2 38.6% of 158.
 <!-- /parity:summary -->
 
 ## Top gaps
@@ -482,6 +482,7 @@ under the UI command that wraps it (a no-op error); the UI command now wins.
 | LR-BEHAV-GPU | GPU acceleration | P0 | ✅ | `crates/gpu/src/render.rs`, `cmd:app.gpu`, `docs/gpu-pipeline.md` | CPU fallback |
 | LR-BEHAV-DRAGDROP | Drag and drop | P1 | ✅ | `crates/ui-egui/src/lib.rs`, `crates/ui-egui/src/panels/grid.rs` (`drag_feedback`), `crates/ui-egui/src/panels/left.rs` (`drop_target`) | files → app (import); grid photos → an album row (adds the selection, with a count badge while dragging) |
 | LR-BEHAV-TOAST | Toast notifications | P1 | ✅ | `crates/ui-egui/src/panels/mod.rs` | |
+| LR-BEHAV-PANEL-RESIZE | Resizable side panels | P1 | ✅ | `crates/ui-egui/src/panels/mod.rs` (`resizable_side`), `crates/ui-egui/src/state.rs` (`LEFT_WIDTH`, `RIGHT_WIDTH`), `crates/ui-egui/src/tests_panels.rs` | drag the left sidebar's right edge (200–480 pt) or the right panel's left edge (250–520 pt); the photo area keeps ≥ 360 pt; widths are kept across panels, views and restarts (`leftWidth` / `rightWidth` in the UI state); the Presets column stays fixed |
 | LR-BEHAV-EMPTY-STATES | Empty states | P1 | ✅ | `crates/ui-egui/src/panels/mod.rs` (`empty_message`) | |
 | LR-BEHAV-TOOLTIPS | Tooltips with shortcuts | P0 | ✅ | `crates/ui-egui/src/panels/bottombar.rs` | |
 | LR-BEHAV-ACCESS | Accessibility | P2 | 🟡 | `crates/ui-egui/src/widgets.rs`, `crates/ui-egui/src/panels/grid.rs` | AccessKit (VoiceOver / Narrator / AT-SPI): sliders announce control and value, buttons / icon buttons / dropdowns / section headers / sources their labels and state, grid thumbnails file name, rating, flag and label; the canvas tools (crop, masks) are pointer-only; not audited with a screen reader |