Dock the results table in the bottom panel

createWebviewPanel only ever lives in the editor area, so the table could
not be dragged next to Terminal / Problems. A WebviewView can, and it can
also be dragged to either side bar.

- Extract ResultsView: the table's html, messaging, row building and
  navigation, independent of what hosts the webview. ReferencePanel keeps
  hosting it in an editor group; ReferenceViewProvider hosts it in a
  contributed panel view container. Results that arrive before the docked
  view has been resolved are queued and applied on resolve.
- coloredReferences.panelLocation selects the placement: bottom (default),
  beside, or below. "below" makes the editor row first so the table is wide
  and short, which suits the column layout better than a tall narrow group.
- sourceColumn() now ignores editors with no view column, so opening a
  reference from the docked view lands in a real editor group.
- toggleView and the refresh button work from either host.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

src/test/suite/panel.test.ts

@@ -57,6 +57,20 @@ async function search(relativeFile: string, declaration: string, symbol: string)
     return { results, position, uri };
 }
 
+function coloredEditorTabs(): vscode.Tab[] {
+    return vscode.window.tabGroups.all.flatMap(g => g.tabs).filter(tab => {
+        const input = tab.input as { uri?: vscode.Uri } | undefined;
+        return input?.uri?.scheme === 'colored-refs';
+    });
+}
+
+async function setPlacement(placement: string): Promise<void> {
+    await vscode.workspace.getConfiguration('coloredReferences')
+        .update('panelLocation', placement, vscode.ConfigurationTarget.Workspace);
+    assert.strictEqual(
+        vscode.workspace.getConfiguration('coloredReferences').get('panelLocation'), placement);
+}
+
 suite('Results panel', () => {
     let results: ReferenceResults;
 
@@ -64,6 +78,8 @@ suite('Results panel', () => {
         const ext = vscode.extensions.getExtension('local.colored-references');
         assert.ok(ext);
         await ext.activate();
+        // These tests cover the editor-area placement; the docked view has its own suite.
+        await setPlacement('beside');
         results = (await search(TARGET_FILE, TARGET_DECL, TARGET_SYMBOL)).results;
     });
 
@@ -138,12 +154,57 @@ suite('Results panel', () => {
         await vscode.commands.executeCommand('coloredReferences.toggleView');
         await sleep(1500);
 
-        const editorTabs = vscode.window.tabGroups.all.flatMap(g => g.tabs).filter(tab => {
-            const input = tab.input as { uri?: vscode.Uri } | undefined;
-            return input?.uri?.scheme === 'colored-refs';
-        });
+        const editorTabs = coloredEditorTabs();
         assert.strictEqual(editorTabs.length, 1, 'expected the results to open in an editor tab');
         assert.ok(editorTabs[0].label.startsWith(`References to ${SECOND_SYMBOL}`),
             `unexpected tab label: ${editorTabs[0].label}`);
     });
 });
+
+suite('Results panel docked in the bottom panel', () => {
+    suiteSetup(async () => {
+        const ext = vscode.extensions.getExtension('local.colored-references');
+        assert.ok(ext);
+        await ext.activate();
+        await setPlacement('bottom');
+
+        // Close the editor-area panels the previous suite left behind.
+        for (const tab of panelTabs()) {
+            await vscode.window.tabGroups.close(tab, true);
+        }
+        for (const tab of coloredEditorTabs()) {
+            await vscode.window.tabGroups.close(tab, true);
+        }
+        await sleep(500);
+    });
+
+    test('the docked view is contributed and focusable', async () => {
+        const commands = await vscode.commands.getCommands(true);
+        assert.ok(commands.includes(`${PANEL_VIEW_TYPE}View.focus`) ||
+            commands.includes('coloredReferences.resultsView.focus'),
+            'the webview view did not contribute a focus command');
+    });
+
+    test('a search fills the docked view instead of opening an editor tab', async () => {
+        await search(TARGET_FILE, TARGET_DECL, TARGET_SYMBOL);
+        await vscode.commands.executeCommand('coloredReferences.findInPanel');
+        await sleep(2000);
+
+        assert.strictEqual(panelTabs().length, 0,
+            'panelLocation is "bottom" but a webview opened in the editor area');
+        assert.strictEqual(coloredEditorTabs().length, 0,
+            'no results document should have been opened');
+    });
+
+    test('toggleView reaches the results held by the docked view', async () => {
+        // Only possible if the docked view actually received the results.
+        await vscode.commands.executeCommand('coloredReferences.toggleView');
+        await sleep(1500);
+
+        const editorTabs = coloredEditorTabs();
+        assert.strictEqual(editorTabs.length, 1,
+            'toggleView could not find the results shown in the docked view');
+        assert.ok(editorTabs[0].label.startsWith(`References to ${TARGET_SYMBOL}`),
+            `unexpected tab label: ${editorTabs[0].label}`);
+    });
+});