feat: multi-component-selector (#1728)

<!-- This is an auto-generated description by cubic. -->
## Summary by cubic
Adds multi-component selection in the preview and sends all selected
components to chat for targeted edits. Updates overlays, UI, and IPC to
support arrays, smarter context focusing, and cross-platform path
normalization.

- **New Features**
- Select multiple components in the iframe; selection mode stays active
until you deactivate it.
- Show a scrollable list of selections with remove buttons and a Clear
all; remove from the list or click an overlay in the preview to
deselect. Sending clears all overlays.
- Separate hover vs selected overlays with labels on hover; overlays
persist after deactivation and re-position on layout changes/resizes.
- Chat input and streaming now send selectedComponents; server builds
per-component snippets and focuses their files in smart context.

- **Migration**
- Replace selectedComponentPreviewAtom with
selectedComponentsPreviewAtom (ComponentSelection[]).
- ChatStreamParams now uses selectedComponents; migrate any
single-selection usages.
  - previewIframeRefAtom added for clearing overlays from the parent.

<sup>Written for commit da0d64cc9e9f83fbf4b975278f6c869f0d3a8c7d.
Summary will update automatically on new commits.</sup>

<!-- End of auto-generated description by cubic. -->

e2e-tests/select_component.spec.ts

@@ -14,11 +14,11 @@ testSkipIfWindows("select component", async ({ po }) => {
     .click();
 
   await po.snapshotPreview();
-  await po.snapshotSelectedComponentDisplay();
+  await po.snapshotSelectedComponentsDisplay();
 
   await po.sendPrompt("[dump] make it smaller");
   await po.snapshotPreview();
-  await expect(po.getSelectedComponentDisplay()).not.toBeVisible();
+  await expect(po.getSelectedComponentsDisplay()).not.toBeVisible();
 
   await po.snapshotServerDump("all-messages");
 
@@ -27,6 +27,34 @@ testSkipIfWindows("select component", async ({ po }) => {
   await po.snapshotServerDump("last-message");
 });
 
+testSkipIfWindows("select multiple components", async ({ po }) => {
+  await po.setUp();
+  await po.sendPrompt("tc=basic");
+  await po.clickTogglePreviewPanel();
+  await po.clickPreviewPickElement();
+
+  await po
+    .getPreviewIframeElement()
+    .contentFrame()
+    .getByRole("heading", { name: "Welcome to Your Blank App" })
+    .click();
+
+  await po
+    .getPreviewIframeElement()
+    .contentFrame()
+    .getByText("Made with Dyad")
+    .click();
+
+  await po.snapshotPreview();
+  await po.snapshotSelectedComponentsDisplay();
+
+  await po.sendPrompt("[dump] make both smaller");
+  await po.snapshotPreview();
+  await expect(po.getSelectedComponentsDisplay()).not.toBeVisible();
+
+  await po.snapshotServerDump("last-message");
+});
+
 testSkipIfWindows("deselect component", async ({ po }) => {
   await po.setUp();
   await po.sendPrompt("tc=basic");
@@ -40,19 +68,50 @@ testSkipIfWindows("deselect component", async ({ po }) => {
     .click();
 
   await po.snapshotPreview();
-  await po.snapshotSelectedComponentDisplay();
+  await po.snapshotSelectedComponentsDisplay();
 
   // Deselect the component and make sure the state has reverted
   await po.clickDeselectComponent();
 
   await po.snapshotPreview();
-  await expect(po.getSelectedComponentDisplay()).not.toBeVisible();
+  await expect(po.getSelectedComponentsDisplay()).not.toBeVisible();
 
   // Send one more prompt to make sure it's a normal message.
   await po.sendPrompt("[dump] tc=basic");
   await po.snapshotServerDump("last-message");
 });
 
+testSkipIfWindows(
+  "deselect individual component from multiple",
+  async ({ po }) => {
+    await po.setUp();
+    await po.sendPrompt("tc=basic");
+    await po.clickTogglePreviewPanel();
+    await po.clickPreviewPickElement();
+
+    await po
+      .getPreviewIframeElement()
+      .contentFrame()
+      .getByRole("heading", { name: "Welcome to Your Blank App" })
+      .click();
+
+    await po
+      .getPreviewIframeElement()
+      .contentFrame()
+      .getByText("Made with Dyad")
+      .click();
+
+    await po.snapshotSelectedComponentsDisplay();
+
+    await po.clickDeselectComponent({ index: 0 });
+
+    await po.snapshotPreview();
+    await po.snapshotSelectedComponentsDisplay();
+
+    await expect(po.getSelectedComponentsDisplay()).toBeVisible();
+  },
+);
+
 testSkipIfWindows("upgrade app to select component", async ({ po }) => {
   await po.setUp();
   await po.importApp("select-component");
@@ -94,7 +153,7 @@ testSkipIfWindows("select component next.js", async ({ po }) => {
     .click();
 
   await po.snapshotPreview();
-  await po.snapshotSelectedComponentDisplay();
+  await po.snapshotSelectedComponentsDisplay();
 
   await po.sendPrompt("[dump] make it smaller");
   await po.snapshotPreview();