refactor(theme): centralize status colors and overlay tints in CSS vars

Introduce semantic theme variables (e.g. --color-success, --color-danger,
--color-warning, --color-info) and a set of overlay/tint/shadow variables
(--app-hover-tint, --app-raise-tint, --app-soft-tint, --app-overlay-shadow,
--app-menu-shadow, --app-float-shadow, etc.) and use them throughout
app.css in place of many hard-coded color, background and shadow values.

This change:
- replaces literal color tokens used for badges, pills, buttons, menus,
  toasts, borders and file icons with the new semantic variables
- switches several box-shadow and overlay usages to the new shadow vars
- harmonizes light-theme surface, border and scrollbar values to explicit
  variables for easier maintenance

No structural or behavioral changes; this is purely a visual/theming
refactor to make future theme adjustments and dark/light parity simpler.

src/lib/components/ResolveDialog.svelte

@@ -368,12 +368,12 @@
   .conflict-workbench button{display:inline-flex;align-items:center;justify-content:center;gap:8px;min-height:30px;padding:5px 10px;border:1px solid var(--color-border-input);border-radius:3px;background:transparent;color:var(--color-ink);font-size:13px;font-weight:400;white-space:nowrap}
   .conflict-workbench button:hover:not(:disabled){background:var(--color-surface-hover);border-color:var(--color-ink-faint)}.conflict-workbench button:disabled{opacity:.45;cursor:default}.conflict-workbench button:focus-visible{outline:2px solid var(--color-accent);outline-offset:-2px}
   .workbench-header{display:flex;align-items:center;justify-content:space-between;gap:16px;min-height:52px;padding:10px 16px;border-bottom:1px solid var(--color-border);background:var(--app-dialog-chrome)}h2{display:flex;align-items:center;gap:10px;margin:0;font-size:15px;font-weight:600}.header-actions{display:flex;gap:12px;align-items:center}.header-actions .close-button{border:0;padding:6px}
-  .workbench-body{display:flex;flex:1;min-height:0}.file-sidebar{display:flex;flex-direction:column;flex:0 0 220px;min-width:0;border-right:1px solid var(--color-border);padding:0 10px}.files-heading{padding:14px 10px 12px;font-size:13px;color:var(--color-ink-muted)}.file-list{flex:1;overflow:auto}.file-sidebar .file-item{display:flex;width:100%;gap:12px;padding:10px 10px;border:1px solid transparent;align-items:flex-start;justify-content:flex-start;text-align:left;white-space:normal}.file-sidebar .file-item.selected{background:var(--color-surface);border-left-color:var(--color-accent)}.file-copy{display:grid;gap:5px;flex:1;min-width:0}.file-copy strong{font-weight:400;overflow:hidden;text-overflow:ellipsis;white-space:nowrap;font-size:13px}.file-copy small{font-size:13px;color:#eda33d}.file-item :global(svg){flex-shrink:0}.open-dot{height:11px;width:11px;background:#eda33d;border-radius:50%;margin-top:5px;flex-shrink:0}.ready,.file-copy small.ready,.file-item :global(svg.ready){color:#68c878}.file-progress{border-top:1px solid var(--color-border);padding:12px 10px;color:var(--color-ink-muted)}
+  .workbench-body{display:flex;flex:1;min-height:0}.file-sidebar{display:flex;flex-direction:column;flex:0 0 220px;min-width:0;border-right:1px solid var(--color-border);padding:0 10px}.files-heading{padding:14px 10px 12px;font-size:13px;color:var(--color-ink-muted)}.file-list{flex:1;overflow:auto}.file-sidebar .file-item{display:flex;width:100%;gap:12px;padding:10px 10px;border:1px solid transparent;align-items:flex-start;justify-content:flex-start;text-align:left;white-space:normal}.file-sidebar .file-item.selected{background:var(--color-surface);border-left-color:var(--color-accent)}.file-copy{display:grid;gap:5px;flex:1;min-width:0}.file-copy strong{font-weight:400;overflow:hidden;text-overflow:ellipsis;white-space:nowrap;font-size:13px}.file-copy small{font-size:13px;color:var(--color-warning)}.file-item :global(svg){flex-shrink:0}.open-dot{height:11px;width:11px;background:var(--color-warning);border-radius:50%;margin-top:5px;flex-shrink:0}.ready,.file-copy small.ready,.file-item :global(svg.ready){color:var(--color-success)}.file-progress{border-top:1px solid var(--color-border);padding:12px 10px;color:var(--color-ink-muted)}
   .conflict-main{display:flex;flex-direction:column;flex:1;min-width:0;min-height:0}.file-header{display:flex;justify-content:space-between;align-items:center;gap:12px;margin:0 10px;padding:10px 6px;border-bottom:1px solid var(--color-border);min-height:48px}.file-header h3{font-size:14px;font-weight:500;overflow:hidden;text-overflow:ellipsis;white-space:nowrap;margin:0}.file-header nav{display:flex;align-items:center;gap:12px;white-space:nowrap}.file-header nav span{margin-right:8px}.file-header nav button{padding:7px 9px}
   .comparison-toolbar{display:flex;gap:10px;align-items:center;padding:8px 12px;flex-wrap:wrap}.comparison-toolbar>span{color:var(--color-ink-muted)}.bulk-actions{display:flex}.bulk-actions>button+button{border-left:0}.comparison-toolbar .manual-button{margin-left:auto;border:0;color:var(--ours);padding-right:0}
   .comparison-scroll{flex:1.25;min-height:150px;overflow:auto;margin:0 10px;border:1px solid var(--color-border)}.comparison-grid{display:grid;grid-template-columns:minmax(0,1fr) minmax(0,1fr);align-content:start;min-width:760px}.side-heading{position:sticky;top:0;z-index:2;background:var(--app-dialog-bg);padding:7px 10px;border-top:2px solid var(--ours);font-size:13px}.theirs-heading{border-color:var(--theirs);border-left:1px solid var(--color-border)}
   .code-line{display:flex;min-width:0;line-height:20px;min-height:20px;font-family:var(--font-mono);font-size:13px}.code-line>span{flex:0 0 44px;text-align:right;padding-right:14px;color:var(--color-ink-faint);user-select:none}.code-line code{font:inherit;white-space:pre;overflow-x:auto;min-width:0;flex:1;padding-right:12px}.incoming-line{border-left:1px solid var(--color-border)}.ours-line{background:color-mix(in srgb,var(--ours) 13%,transparent)}.theirs-line{background:color-mix(in srgb,var(--theirs) 13%,transparent)}.dimmed code{opacity:.45}
-  .conflict-decision{grid-column:1/-1;display:flex;align-items:center;flex-wrap:wrap;gap:10px;padding:7px 10px;border-top:1px solid var(--color-border);border-bottom:1px solid var(--color-border);background:color-mix(in srgb,var(--color-surface) 45%,var(--app-dialog-bg));scroll-margin-top:36px}.conflict-decision strong{font-weight:500;margin-right:12px}.pending{color:#eda33d}.conflict-decision .accept-ours{color:var(--ours);border-color:color-mix(in srgb,var(--ours) 65%,var(--color-border))}.conflict-decision .accept-theirs{color:var(--theirs);border-color:color-mix(in srgb,var(--theirs) 65%,var(--color-border))}.conflict-decision .chosen{background:color-mix(in srgb,var(--ours) 10%,transparent)}.conflict-decision .accept-theirs.chosen{background:color-mix(in srgb,var(--theirs) 10%,transparent)}.decision-label{color:var(--ours);font-size:12px}.both-control{position:relative}.both-menu{position:absolute;right:0;top:100%;z-index:5;min-width:220px;padding:4px;background:var(--app-dialog-chrome);border:1px solid var(--color-border-input);box-shadow:var(--app-panel-shadow)}.both-menu button{width:100%;border:0;text-align:left;justify-content:flex-start}
+  .conflict-decision{grid-column:1/-1;display:flex;align-items:center;flex-wrap:wrap;gap:10px;padding:7px 10px;border-top:1px solid var(--color-border);border-bottom:1px solid var(--color-border);background:color-mix(in srgb,var(--color-surface) 45%,var(--app-dialog-bg));scroll-margin-top:36px}.conflict-decision strong{font-weight:500;margin-right:12px}.pending{color:var(--color-warning)}.conflict-decision .accept-ours{color:var(--ours);border-color:color-mix(in srgb,var(--ours) 65%,var(--color-border))}.conflict-decision .accept-theirs{color:var(--theirs);border-color:color-mix(in srgb,var(--theirs) 65%,var(--color-border))}.conflict-decision .chosen{background:color-mix(in srgb,var(--ours) 10%,transparent)}.conflict-decision .accept-theirs.chosen{background:color-mix(in srgb,var(--theirs) 10%,transparent)}.decision-label{color:var(--ours);font-size:12px}.both-control{position:relative}.both-menu{position:absolute;right:0;top:100%;z-index:5;min-width:220px;padding:4px;background:var(--app-dialog-chrome);border:1px solid var(--color-border-input);box-shadow:var(--app-panel-shadow)}.both-menu button{width:100%;border:0;text-align:left;justify-content:flex-start}
   .result-preview{display:flex;flex:1;min-height:120px;flex-direction:column;margin:10px 10px 0;border:1px solid var(--color-border)}.result-preview header{display:flex;justify-content:space-between;align-items:center;gap:12px;padding:7px 10px;border-bottom:1px solid var(--color-border)}.result-preview strong{font-weight:500;font-size:13px}.preview-code{overflow:auto;flex:1;padding:6px 0}.preview-code code{overflow:visible}.file-actions{display:flex;justify-content:space-between;align-items:center;gap:16px;min-height:48px;padding:8px 12px;border-top:1px solid var(--color-border)}.file-actions>span{color:var(--color-ink-muted)}.file-actions button{background:var(--color-surface)}.workbench-footer{display:flex;align-items:center;justify-content:space-between;gap:20px;padding:10px 16px;border-top:1px solid var(--color-border);min-height:52px}.workbench-footer>span{color:var(--color-ink-muted)}.workbench-footer .apply-button{background:var(--color-primary);border-color:var(--color-primary);color:white;padding:6px 12px;font-weight:500}.workbench-footer .apply-button:hover:not(:disabled){background:var(--color-primary-dark)}
   .empty-message{flex:1;padding:32px;color:var(--color-ink-muted)}.manual-editor{flex:1.25;min-height:150px;resize:none;margin:0 10px;padding:14px;font:13px/20px var(--font-mono);background:var(--app-input-bg);color:var(--color-ink);border:1px solid var(--color-border-input)}.binary-content{flex:1;padding:24px}.binary-content p{display:flex;gap:10px;align-items:center;color:var(--color-ink-muted)}.binary-options{display:flex;gap:16px;margin-top:24px}.binary-options button{flex:1;flex-direction:column;gap:12px;padding:24px;white-space:normal}.binary-options button.chosen{border-color:var(--ours);background:color-mix(in srgb,var(--ours) 10%,transparent)}
   .conflict-backdrop{display:flex;align-items:center;justify-content:center}