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/snapshots/select_component.spec.ts_select-multiple-components-2.aria.yml

@@ -0,0 +1,10 @@
+- text: Selected Components (2)
+- button "Clear all"
+- img
+- text: h1 src/pages/Index.tsx:9
+- button "Deselect component":
+  - img
+- img
+- text: a src/components/made-with-dyad.tsx:4
+- button "Deselect component":
+  - img