feat(dees-table): add opt-in flash highlighting for updated table cells

ts_web/elements/00group-dataview/dees-table/styles.ts

@@ -373,6 +373,72 @@ export const tableStyles: CSSResult[] = [
         line-height: 24px;
       }
 
+      /* ---- Cell flash highlighting (opt-in via highlight-updates="flash") ----
+         Bloomberg/TradingView-style: the text itself briefly takes an accent
+         color then fades back to the default. No background tint, no layout
+         shift, no weight change. Readable, modern, subtle.
+         Consumers can override per instance:
+           dees-table#myTable { --dees-table-flash-color: hsl(142 76% 40%); }
+      */
+      :host {
+        --dees-table-flash-color: ${cssManager.bdTheme(
+          'hsl(32 95% 44%)',
+          'hsl(45 93% 62%)'
+        )};
+        --dees-table-flash-easing: cubic-bezier(0.22, 0.61, 0.36, 1);
+      }
+
+      .innerCellContainer.flashing {
+        animation: dees-table-cell-flash
+                   var(--dees-table-flash-duration, 900ms)
+                   var(--dees-table-flash-easing);
+      }
+
+      /* Hold the accent color briefly, then fade back to the theme's default
+         text color. Inherits to child text and to SVG icons that use
+         currentColor. Cells with explicit color overrides in renderers are
+         intentionally unaffected. */
+      @keyframes dees-table-cell-flash {
+        0%,
+        35% { color: var(--dees-table-flash-color); }
+        100% { color: var(--dees-color-text-primary); }
+      }
+
+      @media (prefers-reduced-motion: reduce) {
+        .innerCellContainer.flashing {
+          animation: none;
+          color: var(--dees-table-flash-color);
+        }
+      }
+
+      /* Dev-time warning banner shown when highlight-updates="flash" but
+         rowKey is missing. Consumers should never ship this to production. */
+      .flashConfigWarning {
+        display: flex;
+        align-items: center;
+        gap: 8px;
+        margin: 8px 16px 0;
+        padding: 8px 12px;
+        border-left: 3px solid ${cssManager.bdTheme('hsl(38 92% 50%)', 'hsl(48 96% 63%)')};
+        background: ${cssManager.bdTheme('hsl(48 96% 89% / 0.6)', 'hsl(48 96% 30% / 0.15)')};
+        color: ${cssManager.bdTheme('hsl(32 81% 29%)', 'hsl(48 96% 80%)')};
+        font-size: 12px;
+        line-height: 1.4;
+        border-radius: 4px;
+      }
+      .flashConfigWarning dees-icon {
+        width: 14px;
+        height: 14px;
+        flex: 0 0 auto;
+      }
+      .flashConfigWarning code {
+        padding: 1px 4px;
+        border-radius: 3px;
+        background: ${cssManager.bdTheme('hsl(0 0% 100% / 0.6)', 'hsl(0 0% 0% / 0.3)')};
+        font-family: ${cssGeistFontFamily};
+        font-size: 11px;
+      }
+
       /* Editable cell affordances */
       td.editable {
         cursor: text;