Move Code editor line numbers setting to Editor and Code Review page

[warp-agent-staging]

Description

Moves the "Code editor line numbers" dropdown setting from the Features page's "Text Editing" category to the "Editor and Code Review" sub-page (under the Code umbrella), per a Slack request from acarl005.

The setting itself is unchanged (Absolute/Relative dropdown backed by AppEditorSettings::code_editor_line_number_mode). The dropdown's ViewHandle, its action variant (SetCodeEditorLineNumberMode), the model subscription that refreshes the dropdown's items/selection, and its telemetry event were all carried over from FeaturesPageView to EditorAndCodeReviewPageView.

The Editor and Code Review page only renders when FeatureFlag::FullSourceCodeEmbedding or FeatureFlag::OpenWarpNewSettingsModes is enabled, and neither is in RELEASE_FLAGS, so a straight move would have made the setting vanish outright on stable builds. To avoid that regression, the Features page keeps its own copy of the widget, gated to render only when the Editor and Code Review page would not be shown (!(FullSourceCodeEmbedding.is_enabled() || OpenWarpNewSettingsModes.is_enabled())) — mirroring the existing AutoOpenCodeReviewPaneWidget dual-registration pattern already used on this page. The setting is reachable in exactly one place in either configuration, never both, never neither.

Both copies' search_terms are identical and now include both "number" and "numbers" so the setting's own label ("Code editor line numbers") matches settings search.

Linked Issue

No tracked issue exists for this change; it originated directly from a Slack request.

Testing

No automated test was added — this is a UI relocation of an existing setting with no behavior change, and the repo's settings-page filter/search behavior already has coverage for the shared PageType machinery this widget reuses.

• ./script/format and cargo clippy -p warp --all-targets --tests -- -D warnings both pass.
• cargo build --bin warp compiles cleanly.
• Manually verified both configurations with the computer-use tool, using a second build with FullSourceCodeEmbedding and OpenWarpNewSettingsModes force-disabled to simulate the stable/flags-off path:
  • Flags on (default build): the setting appears only on Code > Editor and Code Review (as the last item, below "Auto save"); it is absent from the Features page entirely; searching "line numbers" returns exactly 1 result ("Editor and Code Review" under "Code") and navigates to the setting; the dropdown offers Absolute/Relative, changing it updates immediately, and the value persists after navigating away and back.
  • Flags off: the "Code" section/"Editor and Code Review" page does not appear in the sidebar at all; the setting appears only on the Features page's Text Editing section (between "Autocomplete quotes, parentheses, and brackets" and "Edit code and commands with Vim keybindings"); searching "line numbers" returns exactly 1 result ("Features") and navigates to the setting; the dropdown works and persists there too.

Screenshots / Videos

Computer-use video recordings

Testing Code editor line numbers dropdown persistence: Recording navigation to Settings > Code > Editor and Code Review, opening the "Code editor line numbers:" dropdown, selecting a different option, and verifying the change.

Computer-use screenshots (8)

Features settings page (flags-on default build) — the setting is absent here.

Editor and Code Review settings page (flags-on default build) showing the setting in its new home.

Dropdown options on the Editor and Code Review page (flags-on default build).

Settings sidebar with both flags force-disabled: no "Code" section/umbrella present anywhere.

Features page (flags off) showing "Code editor line numbers:" restored in its fallback location.

Features page (flags off), confirming the dropdown selection updates immediately.

Flags-on build: settings search surfaces exactly one result, under Code > Editor and Code Review.

Flags-off build: settings search surfaces exactly one result, under Features.

Agent Mode

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