Improve Android TV accessibility and media handling

[mukulhase]

Summary

• fix D-pad focus transfer from TV text editors to their reproduced neighboring controls
• make the room overflow popup focusable and keep Up/Down navigation within its visible actions
• replace unavailable Android TV document providers with an in-app, D-pad-native local video picker
• add a TV-only Pre-download action that uses four HTTP byte ranges when supported, falls back to a sequential request, and publishes the result to Movies/Syncplay
• allow a connected hardware keyboard to type, edit, and send chat messages while the room UI is locked
• keep a stable incoming-message snapshot during fade-out so a new ineligible message cannot replace or cancel the displayed content

Reproduced issues

The following failures were reproduced on an Android TV API 36 emulator before changing them:

Surface	Failure
Network URL dialog	The editor could not reliably receive initial focus, and Down did not reach the action row after keyboard dismissal.
Home username/room fields	Down stayed in the current editor instead of moving to the next field.
Shared playlist: Add URL	The dialog opened without a focused node, and Down did not reach Done after keyboard dismissal.
Seek To	Left stayed in seconds instead of moving to minutes.
Subtitle search	Right stayed in the search editor because the search action was not focusable.
Managed room name	Down stayed in the editor instead of reaching the actions.
Trusted domains	Down stayed in the editor instead of reaching the actions.
Room overflow	Opening the three-dot menu left focus behind the popup, and Leave room was unreachable with Down.
Local video picker	Android TV reported that no app could handle file selection; the available media-provider grid was also not D-pad focusable.
Fading chat	A later self/seen message could replace the message being animated out and cancel the intended presentation.

Behavior

• Android TV editors route directional input into explicit Compose focus destinations once the IME is no longer handling navigation.
• Popup action controls are real TV focus targets and respond to D-pad Center/Enter.
• The overflow popup takes focus at its first available action, traverses its visible rows, and allows Leave room to be activated.
• Downloaded videos appear in the in-app local picker and can be selected later.
• Entering locked mode immediately dismisses any active IME and transfers focus to a non-editor surface; printable hardware-key events update a compact draft, Backspace edits it, and Enter sends through the existing chat dispatcher.

Verification

• ./gradlew :shared:testAndroidHostTest :androidApp:assembleExoOnlyDebug -PexoOnly=true --no-daemon
• URL editor: Back, Down, Right, Center focused and activated Pre-download
• overflow: initial focus moved to Picture-in-Picture and three Down presses reached Leave room
• parallel download server observed one range probe followed by four concurrent byte-range requests; completion was published as parallel-test.mp4
• the downloaded file appeared in the in-app local picker and was selected successfully
• locking while the chat IME was visible, followed immediately by a raw hardware key, left mInputShown=false, removed the input connection, and updated only the compact locked draft
• locked UI accepted hardware text, removed a full character with Backspace, and sent with Enter
• final APK installed and launched on a paired Google TV Streamer

[yuroyami]

I'll review this soon and include it in the next release shortly