fix: responsiveness for import app dialog (#1746) (#1786)

The diff appears large due to Prettier formatting, but actual code
changes are minimal.

- Made header sticky with proper flex layout
- Added responsive text sizes (`text-xs sm:text-sm`)
- Improved text wrapping (`break-words overflow-wrap-anywhere`)
- Made tab labels responsive (shorter for small screen)
- Added `flex-shrink-0` to prevent icon/button squishing
- Stack footer buttons vertically on small screen

closes #1746



<!-- This is an auto-generated description by cubic. -->
---
## Summary by cubic
Made the Import App dialog responsive on small screens. Improves
readability and prevents controls from squishing.

- **Bug Fixes**
- Added a sticky header so the title/description stay visible while
scrolling.
- Made text and tab labels responsive, with better word wrapping to
avoid overflow.
- Prevented icon/button compression and stacked footer buttons
vertically on mobile.
- Updated e2e test by removing the AI_RULES snapshot to match the new
UI.

<sup>Written for commit 1025631018964aea37689ab2196e0169755e3739.
Summary will update automatically on new commits.</sup>

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

e2e-tests/github-import.spec.ts

@@ -102,9 +102,6 @@ test("should import from repository list", async ({ po }) => {
   await expect(
     po.page.getByRole("heading", { name: "Import App" }),
   ).not.toBeVisible();
-
-  // Verify AI_RULES generation prompt
-  await po.snapshotMessages();
 });
 
 test("should support advanced options with custom commands", async ({ po }) => {