Delete four orphaned input-screen feature flags

[malmstein]

Task/Issue URL: https://app.asana.com/1/137249556945/project/1211654189969294/task/1215377998399622
Tech Design URL (if applicable):
API Proposals URL(s) (if applicable): Pending — see note below.

Description

Deletes four input-screen feature flags that were already orphaned: the flag was still cached into state in RealDuckChat, but nothing read that state once the fullscreen Input Screen was removed (Steps 2 and 3).

Flags removed, with their production reader count before this PR:

Flag	Backing state	Production readers
inputScreenBottomBarSupport	DuckChatInternal.inputScreenBottomBarEnabled	0
showMainButtonsInInputScreen	DuckChatInternal.showMainButtonsInInputScreen	0
showInputScreenAutomaticallyOnNewTab	DuckAiFeatureState.showInputScreenAutomaticallyOnNewTab	0
showInputScreenOnSystemSearchLaunch	DuckAiFeatureState.showInputScreenOnSystemSearchLaunch	0

"Production readers" excludes RealDuckChat itself and tests. Note SystemSearchViewModel no longer reads showInputScreenOnSystemSearchLaunch despite the name, and inputScreenMainButtonsEnabled was assigned in cacheConfig() and never read anywhere.

Also removes the backing MutableStateFlows, the cached fields, the cacheConfig() / cacheUserSettings() reads, the DuckChatInternal declarations, the FakeDuckChatInternal overrides, and the eight RealDuckChatTest tests that only covered these flags.

167 deletions, no additions. No behaviour change — every deleted path was unreachable.

Two of the four flags were surfaced on DuckAiFeatureState in duckchat-api, so this is a deletion-only public API change. Flagging for a decision on whether a removal-only -api delta needs its own API Proposal or can ride along; happy to file one if the team wants it.

Deliberately not in scope, because they still have live readers — these are Step 6b:

• nativeInputField — needs hardcoding to native-on, not deleting
• duckAiInputScreen — still read by DuckChatSettingsViewModel
• DuckAiFeatureState.showInputScreen — still read by BrowserTabViewModel, CtaViewModel and InputScreenDiscoveryFunnel

Steps to test this PR

Nothing should change — this is a regression check

• Build and install the internal variant
• Focus the omnibar and confirm the native input field appears and behaves as before, in both top and bottom omnibar positions
• Open a new tab and confirm the same behaviour as before this PR
• Launch the app from the search widget and confirm the same behaviour as before this PR
• Open Settings > Duck.ai and confirm the input screen toggle still shows and works (duckAiInputScreen is untouched by this PR)

Automated

• ./gradlew :duckchat-impl:testDebugUnitTest — 1850 tests, 0 failures
• ./gradlew :app:compilePlayDebugUnitTestKotlin — confirms no consumer depended on the removed duckchat-api fields

UI changes

Before	After
No UI changes	No UI changes

---

Note

Low Risk
Deletion-only cleanup of dead flags and API surface; no reachable code paths or security/data logic changed.

Overview
Removes four orphaned Duck.ai input-screen remote flags and all code that only fed unreachable state after the fullscreen Input Screen was removed. No new behavior is introduced.

Remote toggles removed from DuckChatFeature: showInputScreenAutomaticallyOnNewTab, showInputScreenOnSystemSearchLaunch, inputScreenBottomBarSupport, and showMainButtonsInInputScreen.

Public API (duckchat-api): DuckAiFeatureState no longer exposes showInputScreenAutomaticallyOnNewTab or showInputScreenOnSystemSearchLaunch.

Implementation: DuckChatInternal drops inputScreenBottomBarEnabled and showMainButtonsInInputScreen; RealDuckChat removes the matching StateFlows, cached fields, and cacheConfig / cacheUserSettings wiring. Tests and FakeDuckChatInternal are updated accordingly.

Runtime impact: None — production had zero readers of these flags outside RealDuckChat and tests.

^{Reviewed by Cursor Bugbot for commit 14fa918. Bugbot is set up for automated code reviews on this repo. Configure here.}

[github-actions]

⚠️ API Proposal reminder

This PR changes the public surface of one or more -api modules, but the API Proposals field of the PR description is empty. This is a non-blocking reminder — please double-check whether a proposal is needed.

Changed -api source files:

• duckchat/duckchat-api/src/main/java/com/duckduckgo/duckchat/api/DuckAiFeatureState.kt

To clear this reminder, edit the PR description and either:

• add the approved API Proposal link(s) in the API Proposals field (one per line), or
• write None there if this PR does not change the public API (e.g. KDoc, comments, tests).

See the API Proposals section in .claude/docs/contributions.md for details.

[joshliebe]

Nice cleanup, LGTM!

[malmstein]

Thanks @joshliebe !