feat(ui): add DataTable and Toaster, drop the legacy Table, fix overlay dialogs

DataTable replaces the 20-line Table scaffold entirely: columns, sorting,
filtering, pagination, selection, bulk actions, comparison layout, sticky
first column, custom HTML cells, and a remote source driven by a `request`
output rather than a function prop (props travel as HTML attributes, so a
function arrives as its own source text).

Toaster replaces the hand-rolled status div: tone icons, actions, hover
pause/resume and a progress bar.

Overlays audit -- Modal and Drawer declared aria-modal="true" but nothing
ever moved focus into the panel, so the @keydown handler on their root
never ran and closeOnEscape did nothing. Focus, focus restore, a Tab trap
and a body scroll lock now live in the reactive runtime, shared by both.

ContextMenu placed pointer menus by subtracting a guessed 340x420 from the
viewport, which pushed every menu that was not that size away from the
pointer; it now positions at the pointer and lets the anchored clamp pull
it back once it can be measured.

The reactive runtime size budget moves 150k -> 175k to cover anchored
overlays, dialog behaviour, the toaster and the DataTable client half.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

scripts/security-performance-audit.mjs

@@ -156,7 +156,11 @@ addCheck(
 );
 
 const runtimeBudgets = {
-  "reactive-runtime.ts": 150_000,
+  // Raised for the 9.0 release: the reactive runtime took on anchored-overlay
+  // clamping, modal dialog focus/scroll behaviour, the toaster and the client
+  // half of DataTable. This is a deliberate ceiling, not a rubber stamp --
+  // raise it again only alongside a decision about what the runtime should own.
+  "reactive-runtime.ts": 175_000,
   "nav-runtime.ts": 25_000,
   "realtime-runtime.ts": 15_000,
 };