feat: show a zoom indicator in the desktop tab bar

[dhh]

Summary

• show a right-aligned ZOOM pill in the desktop tab bar while the focused pane is zoomed, styled like the mode bars (accent background, bold contrast text)
• reserve the pill's width in compute_tab_bar_view so tabs, scroll buttons, the + button, and the overflow ellipsis never render underneath it
• the pill only appears while zoomed, so the tab row is unchanged the rest of the time; the existing per-tab Z label suffix stays for background tabs

The per-tab Z marker is easy to miss when scanning the bar; a fixed-position indicator gives the zoomed state one stable place to look, matching what tmux users get from #{?window_zoomed_flag,ZOOM ,} in status-right.

Testing

• new unit tests: pill renders at the right edge with reserved layout space when the active tab is zoomed, and is absent otherwise
• existing tab bar, mode bar, and full-frame characterization tests pass unchanged

[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: a811aac5-cd96-41d7-8c66-156a5268bd0a

📥 Commits

Reviewing files that changed from the base of the PR and between 0a6cd25 and c570e71.

📒 Files selected for processing (1)

• docs/next/CHANGELOG.md

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

• docs/next/CHANGELOG.md

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📝 Walkthrough

Walkthrough

The desktop tab bar now shows a right-aligned ZOOM indicator when the focused workspace is zoomed. The layout reserves space for the indicator and keeps overflow markers and tab hit areas separate. Tests and the changelog cover the change.

Changes

Desktop tab-bar zoom indicator

Layer / File(s)	Summary
Reserve and render the zoom indicator src/ui/tabs.rs, docs/next/CHANGELOG.md	The tab bar reserves space for the indicator, adjusts overflow placement, renders the styled ZOOM label for zoomed workspaces, and tests visibility, styling, and non-overlap behavior. The changelog documents the new indicator.

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

Possibly related PRs

• herdrdev/herdr#2562: Both changes reserve right-side tab-bar space and prevent overlap with tabs and overflow indicators.
• herdrdev/herdr#2570: Both changes modify tab-bar rendering and layout in src/ui/tabs.rs.
• herdrdev/herdr#2586: Both changes modify tab-bar rendering and reserved right-side status space.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and concisely describes the primary change: adding a zoom indicator to the desktop tab bar.
Description check	✅ Passed	The description directly explains the zoom pill, layout reservation, behavior, styling, and tests covered by the changeset.
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

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[greptile-apps]

Greptile Summary

The PR adds a fixed right-aligned zoom indicator to the desktop tab bar and reserves layout space for it while the active tab is zoomed.

• Adds zoom-aware tab-bar width calculation and indicator rendering.
• Keeps tabs and trailing controls outside the indicator’s reserved area.
• Adds focused rendering and absence tests plus a changelog entry.

Confidence Score: 5/5

The PR appears safe to merge with no actionable defects identified.

The zoom predicate follows the active tab’s state, and the reserved-width rendering path consistently keeps normal tab-bar content outside the indicator.

Important Files Changed

Filename	Overview
src/ui/tabs.rs	Adds zoom-indicator layout, rendering, and tests without an identified actionable defect.
docs/next/CHANGELOG.md	Accurately documents the new desktop tab-bar zoom indicator.

_{Reviews (1): Last reviewed commit: "Merge remote-tracking branch 'upstream/m..." | Re-trigger Greptile}

[ogulcancelik]

superseded by #2586 with the new ui.tab_bar_right