fix(tabs): review fixes for the detailed rail — width-dialog default, compact wrap pass, rich-aware resets

Three review findings on the detailed-rows feature, all in its edge cases:

- The App Settings width select consulted the handheld defaults blob
  (tabRailWidth: 256) BEFORE the rich-aware default, which the renderer
  never reads — so a tablet's unsized rich rail rendered 320 while the
  dialog said 256, and a routine Save persisted the 256 (below the 288px
  tight threshold, permanently). The chain now mirrors
  applyTabRailWidth()'s actual resolution.

- _setTabRailWidth() re-rendered on a compact flip but never re-ran
  applyTabWrapSettings(), the one owner of the folder line, whose railRich
  input reads the compact class this function just toggled. A rich rail
  dragged below 240px kept emitting folder rows — persistently, for a
  stored width < 240, since the boot wrap pass runs before the class is
  first applied. The wrap pass now re-runs on the flip, with exactly one
  render either way.

- Both reset affordances (handle dblclick, Enter on the handle) reset to
  the hardcoded 256 even on a rich rail, landing it below the tight
  threshold; both now resolve the rich-aware default (320), via a new
  optional defaultWidth input on resolveTabRailKeyboardWidth().

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

src/web/public/constants.js

@@ -188,7 +188,9 @@ function resolveTabRailKeyboardWidth(input = {}) {
   let width;
   if (input.key === 'Home') width = TAB_RAIL_MIN_WIDTH;
   else if (input.key === 'End') width = TAB_RAIL_MAX_WIDTH;
-  else if (input.key === 'Enter') width = TAB_RAIL_DEFAULT_WIDTH;
+  // Enter resets to the caller's effective default (the rich rail's is the
+  // Wide preset, not 256 — see _defaultTabRailWidth); absent, the base default.
+  else if (input.key === 'Enter') width = Number(input.defaultWidth) || TAB_RAIL_DEFAULT_WIDTH;
   else if (input.key === 'ArrowLeft' || input.key === 'ArrowRight') {
     const direction = input.key === 'ArrowLeft' ? -1 : 1;
     width = (Number(input.currentWidth) || TAB_RAIL_DEFAULT_WIDTH) + direction * (input.shiftKey ? 32 : 8);