WinDbg plugin, ProcessMemoryWindows, dialog cleanup, and misc fixes

- Add WinDbgMemory plugin with debug server connection support
- Replace ProcessMemory plugin with Windows-specific ProcessMemoryWindows
- Simplify WinDbg dialog: single panel, no tabs, palette-based theming
- Fix example text visibility on dark themes (QPalette::Dark -> Disabled WindowText)
- Fix "file" -> "File" capitalization in source menu
- Add windbg_provider and com_security tests

src/providers/snapshot_provider.h

@@ -1,28 +1,65 @@
 #pragma once
 #include "provider.h"
+#include <QHash>
 #include <memory>
 
 namespace rcx {
 
-// Provider that reads from a cached QByteArray snapshot but delegates
-// metadata (name, kind, getSymbol) to the underlying real provider.
-// Used for async refresh: worker thread reads bulk data into a snapshot,
-// UI thread composes against it without blocking.
+// Page-based snapshot provider.
+//
+// During async refresh the controller reads pages for the main struct and
+// every reachable pointer target.  Compose reads entirely from this page
+// table — no fallback to the real provider, no blocking I/O on the UI
+// thread.  Pages that were never fetched (truly invalid pointers) simply
+// read as zeros.
 class SnapshotProvider : public Provider {
     std::shared_ptr<Provider> m_real;
-    QByteArray m_data;
+    QHash<uint64_t, QByteArray> m_pages;   // page-aligned addr → 4096-byte page
+    int m_mainExtent = 0;                  // logical size of the main struct range
+
+    static constexpr uint64_t kPageSize = 4096;
+    static constexpr uint64_t kPageMask = ~(kPageSize - 1);
 
 public:
-    SnapshotProvider(std::shared_ptr<Provider> real, QByteArray snapshot)
-        : m_real(std::move(real)), m_data(std::move(snapshot)) {}
+    using PageMap = QHash<uint64_t, QByteArray>;
+
+    SnapshotProvider(std::shared_ptr<Provider> real, PageMap pages, int mainExtent)
+        : m_real(std::move(real))
+        , m_pages(std::move(pages))
+        , m_mainExtent(mainExtent) {}
 
     bool read(uint64_t addr, void* buf, int len) const override {
-        if (!isReadable(addr, len)) return false;
-        std::memcpy(buf, m_data.constData() + addr, len);
+        if (len <= 0) return false;
+        char* out = static_cast<char*>(buf);
+        uint64_t cur = addr;
+        int remaining = len;
+        while (remaining > 0) {
+            uint64_t pageAddr = cur & kPageMask;
+            int pageOff = static_cast<int>(cur - pageAddr);
+            int chunk = qMin(remaining, static_cast<int>(kPageSize - pageOff));
+            auto it = m_pages.constFind(pageAddr);
+            if (it != m_pages.constEnd()) {
+                std::memcpy(out, it->constData() + pageOff, chunk);
+            } else {
+                std::memset(out, 0, chunk);
+            }
+            out += chunk;
+            cur += chunk;
+            remaining -= chunk;
+        }
         return true;
     }
 
-    int size() const override { return m_data.size(); }
+    bool isReadable(uint64_t addr, int len) const override {
+        if (len <= 0) return (len == 0);
+        uint64_t end = addr + static_cast<uint64_t>(len);
+        for (uint64_t p = addr & kPageMask; p < end; p += kPageSize) {
+            if (!m_pages.contains(p)) return false;
+        }
+        return true;
+    }
+
+    int size() const override { return m_mainExtent; }
     bool isWritable() const override { return m_real ? m_real->isWritable() : false; }
     bool isLive() const override { return m_real ? m_real->isLive() : false; }
     QString name() const override { return m_real ? m_real->name() : QString(); }
@@ -34,21 +71,36 @@ public:
     bool write(uint64_t addr, const void* buf, int len) override {
         if (!m_real) return false;
         bool ok = m_real->write(addr, buf, len);
-        if (ok && isReadable(addr, len))
-            std::memcpy(m_data.data() + addr, buf, len);
+        if (ok) patchPages(addr, buf, len);
         return ok;
     }
 
-    // Update the entire snapshot (called after async read completes)
-    void updateSnapshot(QByteArray data) { m_data = std::move(data); }
-
-    // Patch specific bytes in the snapshot (called after user writes a value)
-    void patchSnapshot(uint64_t addr, const void* buf, int len) {
-        if (isReadable(addr, len))
-            std::memcpy(m_data.data() + addr, buf, len);
+    // Replace the entire page table (called after async read completes)
+    void updatePages(PageMap pages, int mainExtent) {
+        m_pages = std::move(pages);
+        m_mainExtent = mainExtent;
     }
 
-    const QByteArray& snapshot() const { return m_data; }
+    // Patch specific bytes in existing pages (called after user writes a value)
+    void patchPages(uint64_t addr, const void* buf, int len) {
+        const char* src = static_cast<const char*>(buf);
+        uint64_t cur = addr;
+        int remaining = len;
+        while (remaining > 0) {
+            uint64_t pageAddr = cur & kPageMask;
+            int pageOff = static_cast<int>(cur - pageAddr);
+            int chunk = qMin(remaining, static_cast<int>(kPageSize - pageOff));
+            auto it = m_pages.find(pageAddr);
+            if (it != m_pages.end()) {
+                std::memcpy(it->data() + pageOff, src, chunk);
+            }
+            src += chunk;
+            cur += chunk;
+            remaining -= chunk;
+        }
+    }
+
+    const PageMap& pages() const { return m_pages; }
 };
 
 } // namespace rcx