fix: center tab labels for symmetric highlight padding

[dhh]

Summary

• center tab labels in their cells instead of drawing them left-aligned with a single leading space
• tab cells are label + 4 columns wide, so the old layout put 1 column of highlight before the label and 3 after; the active-tab highlight read as lopsided
• centering splits the padding 2/2 with no change to cell geometry, hit areas, or tab widths

Testing

• new unit test asserts the exact cell content (" omarchy ") for a custom-named tab
• existing tab bar tests pass unchanged; the desktop full-frame characterization digest is updated for the shifted label positions

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro Plus

Run ID: b53e6829-8fd6-4076-a0ee-2708b832b776

📥 Commits

Reviewing files that changed from the base of the PR and between d1244c6 and 8307ce9.

📒 Files selected for processing (2)

• docs/next/CHANGELOG.md
• src/ui/tabs.rs

🚧 Files skipped from review as they are similar to previous changes (1)

• docs/next/CHANGELOG.md

---

📝 Walkthrough

Walkthrough

Desktop tab labels now render centered within their full tab rectangles. Tests cover ASCII and CJK labels. The desktop frame digest and changelog reflect the updated rendering.

Changes

Desktop tab label alignment

Layer / File(s)	Summary
Center tab labels and update validation src/ui/tabs.rs, src/ui/tab_surface.rs, docs/next/CHANGELOG.md	Tab labels use display width to center ASCII and CJK labels. Regression tests cover both cases. The desktop characterization digest and changelog entry are updated.

Estimated code review effort: 2 (Simple) | ~10 minutes

Possibly related PRs

• herdrdev/herdr#2560: Both PRs modify src/ui/tabs.rs tab-bar rendering and tests.
• herdrdev/herdr#2562: Both PRs modify tab-bar layout in src/ui/tabs.rs.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description check	✅ Passed	The description clearly explains the centered tab labels, symmetric padding, unchanged geometry, and related tests.
Title check	✅ Passed	The title clearly and concisely describes the main change: centering tab labels for symmetric highlight padding.
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.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

---

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

[coderabbitai]

Actionable comments posted: 1

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro Plus

Run ID: 35e34e59-129e-40f2-a3f5-3eb6387791e9

📥 Commits

Reviewing files that changed from the base of the PR and between ca1af38 and d1244c6.

📒 Files selected for processing (3)

• docs/next/CHANGELOG.md
• src/ui/tab_surface.rs
• src/ui/tabs.rs

[greptile-apps]

Greptile Summary

The PR centers desktop tab labels using terminal display width while preserving existing tab geometry and hit areas.

• Replaces asymmetric tab-label padding with an even left/right split.
• Adds coverage for ASCII and wide CJK labels.
• Updates the desktop frame characterization digest and changelog.

Confidence Score: 5/5

The PR appears safe to merge.

No blocking failure remains.

Important Files Changed

Filename	Overview
src/ui/tabs.rs	Centers labels by terminal-column width and adds focused regression coverage for ASCII and CJK rendering.
src/ui/tab_surface.rs	Updates the expected desktop semantic-frame digest to reflect shifted label positions.
docs/next/CHANGELOG.md	Documents centered desktop tab labels and symmetric active-tab padding.

_{Reviews (3): Last reviewed commit: "fix: center tab labels by display width,..." | Re-trigger Greptile}