fix: WinDbg provider stops auto-selecting module, new tabs inherit source

- WinDbg provider no longer picks arbitrary module[0] as name/base
  (was showing "WS2_32" for kernel dumps). Name is now generic
  "WinDbg (Live)" / "WinDbg (Dump)", base stays 0 so controller
  doesn't override user's address.
- Added throttled read failure logging to WinDbg provider.
- New tabs (File→New Class, workspace right-click) inherit the
  current tab's source/provider so users don't have to re-attach.
- Updated WinDbg provider tests for new behavior.

src/compose.cpp

@@ -303,6 +303,7 @@ void composeParent(ComposeState& state, const NodeTree& tree,
                 lm.lineKind   = LineKind::Field;
                 lm.nodeKind   = node.elementKind;
                 lm.isArrayElement = true;
+                lm.arrayElementIdx = i;
                 lm.offsetText = fmt::fmtOffsetMargin(elemAddr, false, state.offsetHexDigits);
                 lm.offsetAddr = elemAddr;
                 lm.ptrBase    = state.currentPtrBase;