feat(tabs): add "Show tab numbers" setting (horizontal + vertical tabs)

[ultramcu]

Description

Adds an optional "Show tab numbers" setting (Settings → Appearance → Tabs; default off) that prefixes each tab with its 1‑based position number, making the Cmd+1..9 tab‑switch shortcuts discoverable at a glance. The number is presentation‑only — it is never written into stored tab titles, copied text, or search text.

Works in both layouts:

• Horizontal tabs — TabComponent::render_tab_content prefixes the title ("{n} {title}").
• Vertical tabs — a new tab_number: Option<usize> on PaneProps, set on each tab's representative (first) row only, rendered via a small render_tab_number_label element before the icon. Covers all three view modes (Expanded, Compact, Summary).

The numbering is consistent with the shortcut: tab tabs[0] shows 1 and Cmd+1 activates it (ActivateTabByNumber(n) → tabs[n-1]).

Files

• app/src/workspace/tab_settings.rs — new show_tab_numbers bool (appearance.tabs.show_tab_numbers).
• app/src/tab.rs — horizontal tab rendering.
• app/src/settings_view/appearance_page.rs — Settings UI toggle (mirrors "Show tab indicators").
• app/src/workspace/view.rs — TabSettingsChangedEvent::ShowTabNumbers handler.
• app/src/workspace/view/vertical_tabs.rs — vertical tab rendering.
• specs/GH4028/ — product + tech spec.

Linked Issue

Closes #4028 ("Show Tab number on tabs").

Note for maintainers: #4028 is currently labeled enhancement, triaged but not yet ready-to-spec/ready-to-implement. I've added a product + tech spec under specs/GH4028/ to support the spec flow described in CONTRIBUTING.md. Happy to adjust scope or split the spec into its own PR if you'd prefer — flagging proactively so this can be triaged.

• The linked issue is labeled ready-to-spec or ready-to-implement.

Testing

• Manually tested locally — built an OSS debug bundle, enabled the setting, and confirmed the 1‑based number renders on each vertical tab (and horizontal tabs) and lines up with Cmd+N. The number does not leak into copied tab titles or tab search.

Automated:

• cargo check -p warp — clean.
• cargo test -p warp tab_settings — passing.
• cargo fmt / cargo clippy -p warp --all-targets — clean.

Screenshots / Videos

Agent Mode

• Warp Agent Mode - This PR was created via Warp's AI Agent Mode

CHANGELOG-IMPROVEMENT: Add a "Show tab numbers" setting (Appearance → Tabs) that labels each tab with its Cmd+N switch position, for both horizontal and vertical tabs.

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@ultramcu

This PR is not linked to an issue that is marked with ready-to-implement.

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To continue, link this PR to a same-repo issue such as Closes #123 in the PR description, and make sure that issue has ready-to-implement.

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@ultramcu

This PR is not linked to an issue that is marked with ready-to-implement.

Issue-state enforcement details:

• Associated same-repo issues checked: none

• Required readiness label: ready-to-implement

To continue, link this PR to a same-repo issue such as Closes #123 in the PR description, and make sure that issue has ready-to-implement.

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[ultramcu]

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[ultramcu]

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[ultramcu]

@oss-maintainers This PR implements #4028 ("Show Tab number on tabs"), which is currently labeled enhancement, triaged but not yet ready-to-spec/ready-to-implement.

To support the spec flow in CONTRIBUTING.md, I've added a product + tech spec under specs/GH4028/ describing the behavior invariants and implementation. The change is small and self-contained (opt-in setting, default off, presentation-only), and works for both horizontal and vertical tabs.

Could you take a look and, if it's a direction you're open to, move #4028 to ready-to-spec (for spec review) or ready-to-implement? I'll run /oz-review once the readiness label is in place so I don't burn re-reviews while it's still gated. Happy to split the spec into its own PR or adjust scope if you prefer.