Task #753: revert row spacing in executive meetings table to pre-#747

- User preferred the original row density; reverted the tightening only:
  meeting/attendees/time/merged tbody cells py-1.5→py-3, number cell
  py-1.5→py-2, AttendeesCell split-mode wrapper space-y-1→space-y-2.
- Kept the square corners (#747) and the header-attached-to-table fix
  (!mb-0 on em-sticky-thead, !mt-0 on wrapper from #749/#751).
- tx-os tsc clean; grep confirms no tightened values remain; architect
  review passed.

artifacts/tx-os/src/pages/executive-meetings.tsx

@@ -4434,7 +4434,7 @@ function MeetingRow({
   }, [listeners, effectiveDragEnabled, isSkipDragTarget]);
 
   const numberCellCls =
-    "border border-gray-300 px-2 py-1.5 text-center align-middle font-semibold " +
+    "border border-gray-300 px-2 py-2 text-center align-middle font-semibold " +
     (highlight || isCancelled
       ? "bg-red-600 text-white"
       : "bg-white text-[#0B1E3F]");
@@ -4637,7 +4637,7 @@ function MeetingRow({
         return (
           <td
             key="meeting"
-            className={`border border-gray-300 px-3 py-1.5 align-middle text-center ${meeting.isExternal ? "text-[#dc2626]" : "text-[#0B1E3F]"} relative group`}
+            className={`border border-gray-300 px-3 py-3 align-middle text-center ${meeting.isExternal ? "text-[#dc2626]" : "text-[#0B1E3F]"} relative group`}
             style={tintedCellStyle(col, true)}
           >
             <EditableCell
@@ -4670,7 +4670,7 @@ function MeetingRow({
         return (
           <td
             key="attendees"
-            className="border border-gray-300 px-3 py-1.5 align-middle text-center relative group"
+            className="border border-gray-300 px-3 py-3 align-middle text-center relative group"
             style={tintedCellStyle(col, false)}
           >
             <AttendeesCell
@@ -4691,7 +4691,7 @@ function MeetingRow({
         return (
           <td
             key="time"
-            className="border border-gray-300 px-3 py-1.5 align-middle text-center relative group"
+            className="border border-gray-300 px-3 py-3 align-middle text-center relative group"
             style={tintedCellStyle(col, false)}
           >
             <TimeRangeCell
@@ -4732,7 +4732,7 @@ function MeetingRow({
           <td
             key="merge"
             colSpan={span}
-            className="border border-gray-300 px-3 py-1.5 align-middle text-[#0B1E3F] relative group"
+            className="border border-gray-300 px-3 py-3 align-middle text-[#0B1E3F] relative group"
             style={{
               width: totalWidth,
               overflow: "hidden",
@@ -5650,7 +5650,7 @@ function AttendeesCell({
     // suppress its own trailing subheading chip. Per-group "+" person
     // chips and the after-section chips are unaffected.
     return (
-      <div className="space-y-1">
+      <div className="space-y-2">
         {(virtual.length > 0 || isPendingForType("virtual")) && (
           <AttendeeGroup
             label={