fix(panel): task-detail tab state in URL, nav placement, kanban overflow, sidebar divider, tooltip sweep

- Task detail: active tab lives in ?tab= (survives reload, back/forward, and
  prev/next task jumps); prev/next arrows move into the header row next to
  Actions instead of their own row above the title
- Constraints section always starts collapsed (project boilerplate)
- Kanban: native overflow scroll replaces Radix ScrollArea (display:table
  viewport let cards grow past the column and clip); columns share width
  (flex-1, 18rem floor, 24rem cap); dark column colors normalized to /40 tints
- Sidebar footer: drop the Separator doubled with the wrapper's border-t
- Tooltips: self-providing Tooltip root (300ms) + hover hints across sidebar,
  header, task detail, kanban, and every icon-only button that had none

panel/src/components/kanban/views/pr-review-kanban.tsx

@@ -12,19 +12,19 @@ const PR_REVIEW_COLUMNS = [
     id: "awaiting",
     status: TaskStatus.AWAITING_PR_REVIEW,
     title: "Awaiting Review",
-    color: "bg-teal-100 dark:bg-teal-900",
+    color: "bg-teal-100 dark:bg-teal-900/40",
   },
   {
     id: "passed",
     status: TaskStatus.AWAITING_PM_REVIEW,
     title: "Passed",
-    color: "bg-green-50 dark:bg-green-950",
+    color: "bg-green-50 dark:bg-green-950/40",
   },
   {
     id: "changes",
     status: TaskStatus.NEEDS_REVISION,
     title: "Changes Requested",
-    color: "bg-red-50 dark:bg-red-950",
+    color: "bg-red-50 dark:bg-red-950/40",
   },
 ];