fix(desktop): toggle fullscreen on plain F

[Kundhan007]

Summary

Binds plain F (no modifiers) to the existing desktop fullscreen toggle in the Compose Window(onKeyEvent = ...) scope in Main.kt, complementing the plain-F binding in the player webview that already landed via #594 (see controls.js on Dev). No other behavior touched.

Note on scope change: this PR originally also bound plain F inside the player webview (controls.js). That half was merged independently via #594, so after rebasing on Dev this PR now contains only the Main.kt window-level handler — the part still uncovered by #594: F works outside the player (library/home screens) and when no Compose node holds focus.

PR type

• Behavior bug/regression fix

Why

Pressing F in the desktop app did nothing outside the player webview, while every major video player (YouTube, VLC, IINA) and mpv itself — which Nuvio's player is built on — toggles fullscreen on F. The desktop shell swallows a key its own engine binds by default, so this restores intended fullscreen/keyboard behavior app-wide.

Desktop scope

macOS desktop app (verified on macOS arm64). Main.kt is shared desktop shell code: the window-level binding applies to the whole app window. No Android/iOS code touched, no changes to controls.js in this PR.

Issue or approval

Fixes #607

UI / behavior impact

• No UI change
• Behavior changed only to fix a documented bug/regression

Policy check

• I have read and understood CONTRIBUTING.md.
• This PR is small, focused, and limited to one problem.
• This PR is scoped to the desktop app, desktop packaging, desktop documentation, or shared code required for desktop behavior.
• This PR is not cosmetic-only.
• Any UI change fixes a linked glitch/bug and includes visual proof, or this PR has no UI change.
• Any behavior change fixes a linked bug/regression or has explicit approval, or this PR has no behavior change.
• This PR does not bundle unrelated refactors, cleanups, formatting, or drive-by changes.
• This PR does not add dependencies, architecture changes, migrations, or product-direction changes without explicit approval.
• I listed the testing performed below.

Scope boundaries

Intentionally not changed: F11 and Cmd+Ctrl+F bindings, Shift+F (rejected for parity), the player webview controls.js plain-F binding (already merged via #594), DesktopAppFullscreen.kt dispatcher, Windows native emulation, signing/packaging, any visual styling.

Testing

• ./gradlew :composeApp:compileKotlinDesktop → BUILD SUCCESSFUL, zero errors (Temurin JDK 17.0.20.1, macOS arm64), against latest Dev including feat(Player Shortcuts): Add the shortcut control functionality to player controls #594.
• Manual (macOS arm64): F toggles fullscreen on library/home/player; f still types in search boxes; modal open = no-op; hold-F = single toggle (400 ms debounce); F on fresh launch before any click toggles; F11 and Cmd+Ctrl+F regressed OK; plain F inside the player continues to work via the feat(Player Shortcuts): Add the shortcut control functionality to player controls #594 webview binding.

Proof video (posted in comments): stock build (F does nothing) vs this build (F toggles fullscreen on macOS arm64).

Breaking changes

None.

Linked issues

Fixes #607

[Kundhan007]

F.full.screen.mp4

please see the video for proof

[Kundhan007]

@KhooLy — rebased this PR on the latest Dev and trimmed its scope to keep it small and focused:

• Dropped the controls.js hunk — plain-F fullscreen inside the player webview already landed via feat(Player Shortcuts): Add the shortcut control functionality to player controls #594 (plus the follow-up text-entry-guard fix), so keeping it would have duplicated that logic and conflicted with it.
• Kept only the Main.kt window-level handler — the part feat(Player Shortcuts): Add the shortcut control functionality to player controls #594 does not cover: F toggles app fullscreen outside the player (library/home) and when no Compose node holds focus, with a 400 ms debounce and modifier guards so typing f in inputs is unaffected. Inside the player, the feat(Player Shortcuts): Add the shortcut control functionality to player controls #594 webview binding continues to serve F.

PR description updated to match. Re-verified after the rebase: ./gradlew :composeApp:compileKotlinDesktop → BUILD SUCCESSFUL against latest Dev (Temurin 17, macOS arm64). This still fixes #607 together with #594. Happy to adjust anything.