Provider refactor: 2-method base class, ProcessProvider, ProcessPicker

Collapse Provider interface from 9 virtual methods to 2 (read + size),
move providers to src/providers/, add name()/kind()/getSymbol() virtuals.
Replace FileProvider with BufferProvider, add ProcessProvider (Win32)
with module-based symbol resolution, wire ProcessPicker dialog, and
integrate getSymbol into pointer display and command row.

- Fix isReadable overflow for large addresses
- Guard deferred showSourcePicker/showTypeAutocomplete against stale edits
- 7/7 tests pass including 3 new provider test suites

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

tests/test_command_row.cpp

@@ -0,0 +1,139 @@
+#include <QTest>
+#include <QString>
+#include <memory>
+#include "providers/provider.h"
+#include "providers/buffer_provider.h"
+#include "providers/null_provider.h"
+
+using namespace rcx;
+
+// -- Replicate the label-building logic from updateCommandRow so we can test it
+//    without needing a full RcxController/RcxDocument/RcxEditor stack.
+
+static QString buildSourceLabel(const Provider& prov) {
+    QString provName = prov.name();
+    if (provName.isEmpty())
+        return QStringLiteral("<Select Source>");
+    return QStringLiteral("%1 '%2'").arg(prov.kind(), provName);
+}
+
+static QString buildCommandRow(const Provider& prov, uint64_t baseAddress) {
+    QString src = buildSourceLabel(prov);
+    QString addr = QStringLiteral("0x") +
+        QString::number(baseAddress, 16).toUpper();
+    return QStringLiteral("   %1 Address: %2").arg(src, addr);
+}
+
+// -- Replicate commandRowSrcSpan for testing
+struct TestColumnSpan {
+    int start = 0;
+    int end = 0;
+    bool valid = false;
+};
+
+static TestColumnSpan commandRowSrcSpan(const QString& lineText) {
+    int idx = lineText.indexOf(QStringLiteral(" Address: "));
+    if (idx < 0) return {};
+    int start = 0;
+    while (start < idx && !lineText[start].isLetterOrNumber()
+           && lineText[start] != '<') start++;
+    if (start >= idx) return {};
+    return {start, idx, true};
+}
+
+class TestCommandRow : public QObject {
+    Q_OBJECT
+
+private slots:
+
+    // ---------------------------------------------------------------
+    // Source label text
+    // ---------------------------------------------------------------
+
+    void label_nullProvider_showsSelectSource() {
+        NullProvider p;
+        QCOMPARE(buildSourceLabel(p), QStringLiteral("<Select Source>"));
+    }
+
+    void label_bufferNoName_showsSelectSource() {
+        // BufferProvider with empty name also triggers <Select Source>
+        BufferProvider p(QByteArray(4, '\0'));
+        QCOMPARE(buildSourceLabel(p), QStringLiteral("<Select Source>"));
+    }
+
+    void label_bufferWithName_showsFileAndName() {
+        BufferProvider p(QByteArray(4, '\0'), "dump.bin");
+        QCOMPARE(buildSourceLabel(p), QStringLiteral("File 'dump.bin'"));
+    }
+
+    // ---------------------------------------------------------------
+    // Full command row text
+    // ---------------------------------------------------------------
+
+    void row_nullProvider() {
+        NullProvider p;
+        QString row = buildCommandRow(p, 0);
+        QCOMPARE(row, QStringLiteral("   <Select Source> Address: 0x0"));
+    }
+
+    void row_fileProvider() {
+        BufferProvider p(QByteArray(4, '\0'), "test.bin");
+        QString row = buildCommandRow(p, 0x140000000ULL);
+        QCOMPARE(row, QStringLiteral("   File 'test.bin' Address: 0x140000000"));
+    }
+
+    // ---------------------------------------------------------------
+    // Source span parsing
+    // ---------------------------------------------------------------
+
+    void span_selectSource() {
+        QString row = buildCommandRow(NullProvider{}, 0);
+        auto span = commandRowSrcSpan(row);
+        QVERIFY(span.valid);
+        QString extracted = row.mid(span.start, span.end - span.start);
+        QCOMPARE(extracted, QStringLiteral("<Select Source>"));
+    }
+
+    void span_fileProvider() {
+        BufferProvider p(QByteArray(4, '\0'), "dump.bin");
+        QString row = buildCommandRow(p, 0x140000000ULL);
+        auto span = commandRowSrcSpan(row);
+        QVERIFY(span.valid);
+        QString extracted = row.mid(span.start, span.end - span.start);
+        QCOMPARE(extracted, QStringLiteral("File 'dump.bin'"));
+    }
+
+    void span_processProvider_simulated() {
+        // Simulate a process provider without needing Windows APIs
+        // by building the string directly
+        QString row = QStringLiteral("   Process 'notepad.exe' Address: 0x7FF600000000");
+        auto span = commandRowSrcSpan(row);
+        QVERIFY(span.valid);
+        QString extracted = row.mid(span.start, span.end - span.start);
+        QCOMPARE(extracted, QStringLiteral("Process 'notepad.exe'"));
+    }
+
+    // ---------------------------------------------------------------
+    // Provider switching simulation
+    // ---------------------------------------------------------------
+
+    void switching_nullToFileToProcess() {
+        // Start with NullProvider
+        std::unique_ptr<Provider> prov = std::make_unique<NullProvider>();
+        QCOMPARE(buildSourceLabel(*prov), QStringLiteral("<Select Source>"));
+
+        // User loads a file
+        prov = std::make_unique<BufferProvider>(QByteArray(64, '\0'), "game.exe");
+        QCOMPARE(buildSourceLabel(*prov), QStringLiteral("File 'game.exe'"));
+
+        // User switches to a "process" -- simulate with a named BufferProvider
+        // (ProcessProvider needs Windows, but the label logic is the same)
+        prov = std::make_unique<BufferProvider>(QByteArray(64, '\0'), "notepad.exe");
+        // BufferProvider kind is "File", but the switching mechanism works the same
+        QCOMPARE(prov->kind(), QStringLiteral("File"));
+        QCOMPARE(prov->name(), QStringLiteral("notepad.exe"));
+    }
+};
+
+QTEST_MAIN(TestCommandRow)
+#include "test_command_row.moc"