Enhance tables canvas reading states

docs/tables_frontend_overhaul_implementation_plan.md

@@ -65,6 +65,7 @@ It is intentionally implementation-focused:
 | 2026-03-21 | P3.2 | Completed | Replaced the floating table picker with a permanent left-rail layout, converted the old selector component into a real page header, and kept the current selection flow intact inside the new reference frame. |
 | 2026-03-21 | P3.3 | Completed | Added rail search, family filters, pinned and recent sections, curated status chips, and keyboard up/down plus Enter handling on top of the new permanent table index rail. |
 | 2026-03-21 | P3.4 | Completed | Added a sticky context bar with reference-mode tabs, variant and severity selectors, roll-jump state, and active filter chips, then wired those controls into page state and canvas filtering. |
+| 2026-03-21 | P3.5 | Completed | Reworked the canvas with sticky headers, a sticky roll-band column, row and column emphasis driven by selection and roll-jump state, selected-cell treatment, and a comfortable/dense density toggle. |
 
 ### Lessons Learned
 
@@ -99,6 +100,7 @@ It is intentionally implementation-focused:
 - The `Tables` navigation model needs its own persistent geometry before advanced behaviors land. Converting the selector to a real rail first keeps later search and keyboard work from being tangled up with another structural rewrite.
 - Rail keyboard behavior is easiest to maintain when it works from one deduplicated option order, even if the UI shows multiple sections. Keeping one internal option list avoids separate arrow-key state per section.
 - The context bar controls should own one shared view-state model before the canvas gets more visual treatment. Wiring the filters into the host page now avoids a second refactor when row, column, and cell emphasis land.
+- Canvas emphasis becomes maintainable once selection, roll-jump, and density are all fed through one explicit state model. That lets the grid respond to context without hiding selection logic inside CSS-only heuristics.
 
 ## Target Outcomes
 
@@ -463,7 +465,7 @@ Build the shared interaction infrastructure needed by multiple destinations befo
 | `P3.2` | Completed | The old dropdown picker is gone; `/tables` now uses a permanent left rail and a real page header while keeping the current selection flow intact. |
 | `P3.3` | Completed | The rail now supports search-as-you-type, family filters, pinned and recent sections, curated status chips, and a deduplicated arrow/Enter keyboard path. |
 | `P3.4` | Completed | The table surface now has a sticky context bar with mode tabs, variant/severity focus, roll-jump state, and active filter chips wired into host-page view state. |
-| `P3.5` | Pending | Rework the canvas for sticky headers, sticky roll bands, stronger reading emphasis, and density control. |
+| `P3.5` | Completed | The canvas now supports sticky headers and roll bands, row and column emphasis from selection and roll-jump state, selected-cell treatment, and a comfortable/dense density toggle. |
 | `P3.6` | Pending | Remove visible resting-state action stacks from non-selected cells. |
 | `P3.7` | Pending | Add the desktop selection-driven inspector. |
 | `P3.8` | Pending | Add the mobile bottom-sheet inspector variant. |