test(e2e): tab selection survives a state-triggered rerun

[sudo-vaibhav]

What

Adds an e2e test proving that tab selection sticks across a rerun when the rerun is ordered by a state change inside a tab.

• examples/demo/src/pages/tabs.ts — new /tabs demo page. A 2-tab layout where tab 2 owns a text_input; committing it reruns the script. Each tab echoes its own state so the spec can confirm the rerun actually fired.
• Registered the page: route + sidebar link in main.ts, export in pages/index.ts.
• e2e/tabs.spec.ts — the spec: default on tab 1 → switch to tab 2 → fill input → Enter → assert the echo updates (rerun landed) and tab 2 is still data-state="active" while tab 1 is inactive. Since Radix unmounts inactive tab content, the input staying visible is an independent confirmation tab 2 held.

Why it sticks

The active tab is uncontrolled Radix state (Tabs defaultValue="0"). On rerun the client patches the tree into a new object ref, but Frame renders every node with a stable key={path} — the tabs path is unchanged, so React preserves the instance and Radix's selection survives. No remount → no snap-back to tab 1. The genuine corner case (the active tab disappears as a result of the state change) would legitimately remount and reset; that's out of scope and noted in the page comment.

Verification

• tabs.spec.ts: 2 passed
• sidebar.spec.ts + smoke.spec.ts (guard against the new nav link breaking counts): 11 passed

🤖 Generated with Claude Code

Summary by CodeRabbit

• New Features

  • Added a Tabs demo page to the example application showcasing tab functionality.

• Tests

  • Added end-to-end tests verifying that tab state persists correctly during server-side reruns.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: ASSERTIVE

Plan: Pro Plus

Run ID: 968c8635-432d-4694-8d51-830bba041e76

📥 Commits

Reviewing files that changed from the base of the PR and between 2131ef4 and a03bfb2.

📒 Files selected for processing (4)

• e2e/tabs.spec.ts
• examples/demo/src/main.ts
• examples/demo/src/pages/index.ts
• examples/demo/src/pages/tabs.ts

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📝 Walkthrough

Walkthrough

A new backroadTabsExample demo page is added with a two-tab Backroad layout; the second tab has a text input that drives a greeting after rerun. The demo is registered in the pages map, sidebar navigation, and router. A Playwright e2e spec verifies that the active tab and input persist after the server-side rerun.

Changes

Tabs Demo Page and E2E Test

Layer / File(s)	Summary
Tabs demo implementation and wiring examples/demo/src/pages/tabs.ts, examples/demo/src/pages/index.ts, examples/demo/src/main.ts	backroadTabsExample defines a two-tab layout where the second tab's text input stores a name and renders a greeting; it is imported and registered in the pages map, and main.ts adds the /tabs sidebar link and route binding.
E2E test for tab state persistence e2e/tabs.spec.ts	Playwright spec navigates to /tabs, verifies the initial active tab, switches to the second tab, fills the input with "Ada," presses Enter to trigger a rerun, then asserts the greeting updates and the second tab remains active with the input still visible.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~5 minutes

Poem

🐇 Two tabs sit side by side,
I click the second — what a ride!
I type my name, press Enter tight,
The server reruns, all feels right.
The tab stays put — hooray, hooray!
Ada gets her greeting today. 🎉

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The PR title directly describes the main change: an e2e test verifying tab selection persistence across reruns, which matches the primary purpose of the changeset.
Description check	✅ Passed	The PR description is comprehensive and addresses all required template sections including Summary, Type of change (test), Test plan, and verification results.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch test/tabs-rerun-state-stick

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_{Comment @coderabbitai help to get the list of available commands.}

[github-actions]

Knip dead-code gate — no regressions

Category	Baseline	Current	Δ
binaries	0	0	±0
catalog	0	0	±0
dependencies	28	28	±0
devDependencies	8	8	±0
duplicates	3	3	±0
enumMembers	0	0	±0
exports	5	5	±0
files	6	6	±0
namespaceMembers	0	0	±0
optionalPeerDependencies	0	0	±0
owners	18	18	±0
types	2	2	±0
unlisted	2	2	±0
unresolved	1	1	±0

All counts at or below baseline.

[github-actions]

size-limit report 📦

Path	Size
backroad-frontend — main JS bundle	296.33 KB (0%)
backroad-frontend — main CSS bundle	14 KB (0%)
backroad-frontend — /signin chunk (lazy)	106.96 KB (0%)