feat: disasm popup, symbol separation, context menu improvements, RVA fixes

- Add Fadec x86 disassembler with hover popup for FuncPtr/void Pointer nodes
- Separate pointer symbol from address: // prefix, green comment coloring,
  independent hover/click zones (address triggers popup, symbol is passive)
- Fix RVA margin and inline local offset for pointer-expanded vtable children
  using ptrBase field threaded through composition
- Expand multi-select context menu with quick-convert, duplicate, copy address
- Remove Edit Value from hex node context menu
- Fix heatmap flickering on hex nodes (remove per-byte alternation)
- Fix popup repositioning when moving mouse between lines
- Truncate disasm popup to 6 lines with ... indicator
- Add BUILD_UI_TESTS option to skip widget tests on headless CI
- Add test_disasm with 35 test cases for disassembly and hex dump
- Add KUSER_SHARED_DATA example .rcx file

src/core.h

@@ -487,6 +487,7 @@ struct LineMeta {
     int      arrayElementIdx = -1; // Index of this element within parent array (-1 if not array element)
     QString  offsetText;
     uint64_t offsetAddr     = 0;     // Raw absolute address (for margin toggle)
+    uint64_t ptrBase        = 0;     // Pointer expansion base (non-zero = use for RVA)
     uint32_t markerMask     = 0;
     bool     dataChanged    = false;  // true if any byte in this node changed since last refresh
     int      heatLevel      = 0;     // 0=static, 1=cold, 2=warm, 3=hot (from ValueHistory)