Highlight script row on add-cue button hover (#1081)

[Tim020]

Summary

• Adds a subtle light-gray row highlight when hovering the add-cue (+) button in the cue editor, clarifying which script line the new cue will be attached to
• Applied to both Vue 2 (client/) and Vue 3 (client-v3/) for parity
• Implemented with pure CSS :has() — no JS state or event handlers needed

Implementation

Added line-row class to the script row and add-cue-btn class to the add-cue button in both ScriptLineCueEditor.vue components, then used a scoped CSS rule:

.line-row:has(.add-cue-btn:hover) {
  background-color: rgba(255, 255, 255, 0.06);
  border-radius: 4px;
  transition: background-color 0.15s ease;
}

Test plan

• Verified hover highlight appears on the correct row in Vue 3 (/ui-new/) using Playwright
• Verified hover highlight appears on the correct row in Vue 2 (/ui/) using Playwright
• npm run lint passes on both clients
• npm run typecheck passes on both clients
• Both frontend builds succeed

Closes #1081

🤖 Generated with Claude Code

[github-actions]

Client V3 Test Results

23 tests  ±0   23 ✅ ±0   0s ⏱️ ±0s
 2 suites ±0    0 💤 ±0 
 1 files   ±0    0 ❌ ±0 

Results for commit fb3f014. ± Comparison against base commit 7b0d256.

[github-actions]

Client Test Results

128 tests  ±0   128 ✅ ±0   0s ⏱️ ±0s
  6 suites ±0     0 💤 ±0 
  1 files   ±0     0 ❌ ±0 

Results for commit fb3f014. ± Comparison against base commit 7b0d256.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[github-actions]

Python Test Results

  1 files  ±0    1 suites  ±0   1m 34s ⏱️ +7s
603 tests ±0  603 ✅ ±0  0 💤 ±0  0 ❌ ±0 
608 runs  ±0  608 ✅ ±0  0 💤 ±0  0 ❌ ±0 

Results for commit fb3f014. ± Comparison against base commit 7b0d256.