fix(bottom-nav-bar): enforce scoping of the nav bar to mobile only

[ShaanNarendran]

Purpose / Description

Scopes the bottom navigation bar to mobile, earlier there was bleeding to tablet still.

Fixes

• For GSoC 2026: Redesign Deck Picker

Approach

Enforced the dev preference so that it does not show for tablets, made sure the switch is hidden on tablets and finally made sure hierarchy lines only work for bottom nav bar enabled devices.

How Has This Been Tested?

Manually tested.

Checklist

Please, go through these checks before submitting the PR.

• You have a descriptive commit message with a short title (first line, max 50 chars).
• You have commented your code, particularly in hard-to-understand areas
• You have performed a self-review of your own code
• UI changes: include screenshots of all affected screens (in particular showing any new or changed strings)
• UI Changes: You have tested your change using the Google Accessibility Scanner

[david-allison]

Knowing whether the table is being used is tricky.

Consider scoping your checks to DeckPicker via a context receiver/parameter, so you can just check if the fragment is visible

[github-actions]

Snapshot diff report: Previous regressions were resolved by the latest commit.

[sanjaysargam]

Enforced the dev preference so that it is always false

This line looks incorrect can be misread, cuz the pref is actually hidden and gated
Rest looks good to me. Tested on Pixel 10 Pro Fold

[david-allison]

LGTM, one nit:

Subject: [PATCH] fix(preferences): hide bottom nav if unavailable
---
Index: AnkiDroid/src/main/java/com/ichi2/anki/preferences/HeaderFragment.kt
IDEA additional info:
Subsystem: com.intellij.openapi.diff.impl.patch.CharsetEP
<+>UTF-8
===================================================================
diff --git a/AnkiDroid/src/main/java/com/ichi2/anki/preferences/HeaderFragment.kt b/AnkiDroid/src/main/java/com/ichi2/anki/preferences/HeaderFragment.kt
--- a/AnkiDroid/src/main/java/com/ichi2/anki/preferences/HeaderFragment.kt	(revision f999adfb8878bf72f706782a5f98d01611b6d625)
+++ b/AnkiDroid/src/main/java/com/ichi2/anki/preferences/HeaderFragment.kt	(revision e02eda0887a518032b29a6155978e09d663d3b6b)
@@ -195,6 +195,9 @@
                 if (BuildConfig.DEBUG) {
                     searchConfiguration.ignorePreference(activity.getString(R.string.developer_options_enabled_by_user_key))
                 }
+                if (!activity.resources.getBoolean(R.bool.bottom_navigation_available)) {
+                    searchConfiguration.ignorePreference(activity.getString(R.string.dev_bottom_nav_key))
+                }
             }
 
             // From [HeaderFragment.onCreatePreferences]

[ShaanNarendran]

Enforced the dev preference so that it is always false

This line looks incorrect can be misread, cuz the pref is actually hidden and gated Rest looks good to me. Tested on Pixel 10 Pro Fold

Edited!