Fix process memory provider base address sync and live refresh

Provider base address now stays in sync with tree base address when
changed via ChangeBase command, fixing reads from arbitrary memory
regions like KUSER_SHARED_DATA at 0x7FFE0000. ReadProcessMemory
handles partial reads gracefully. Snapshot extent uses tree-based
calculation instead of provider size to avoid oversized reads.
MCP source.switch gains pid parameter for programmatic process attach.
MCP server starts by default with logging and slow mode support.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

plugins/ProcessMemory/ProcessMemoryPlugin.h

@@ -25,6 +25,10 @@ public:
     QString kind() const override { return QStringLiteral("LocalProcess"); }
     QString getSymbol(uint64_t addr) const override;
 
+    bool isLive() const override { return true; }
+    uint64_t base() const override { return m_base; }
+    void setBase(uint64_t b) override { m_base = b; }
+
     // Process-specific helpers
     uint32_t pid() const { return m_pid; }
     uint64_t baseAddress() const { return m_base; }