feat(tao): forward back/forward mouse buttons to Compose

[skyecodes]

🚀 Description

Passes the mouse back/forward side buttons through to Compose as PointerButton.Back / PointerButton.Forward on the Tao backend.

Kotlin

• TaoMouseButton: adds BACK = 3 and FORWARD = 4, and moves OTHER from 3 to 5.
• AbstractTaoComposeSceneHost.mapButton and TaoPopupSceneLayerLinux: map the new codes to PointerButton.Back / PointerButton.Forward.

Native

• events.rs: the Rust MOUSE_BUTTON_* codes now match Kotlin (BACK = 3, FORWARD = 4, OTHER = 5). MouseButton::Other(n) is mapped per OS: Windows XBUTTON1/XBUTTON2 (1/2), Linux GDK buttons 8/9, macOS NSEvent.buttonNumber 3/4.
• Vendored tao (macOS): otherMouseDown: / otherMouseUp: read NSEvent.buttonNumber instead of always reporting Middle.
• nucleus_tao_linux_widget.c: the NativeView capture boxes map GDK buttons 8/9 to back/forward. Before, the raw number went through and Kotlin treated it as a Primary click.

Tests / API

• TaoMouseButtonWireDriftTest (new): fails if the events.rs MOUSE_BUTTON_* values and TaoMouseButton stop matching.
• API dump updated for the new TaoMouseButton.BACK / FORWARD fields.

Not covered: the X11/macOS native popup panels (WIRE_BUTTON_*) and the Windows NativeView blending overlay still only handle primary/secondary/tertiary, so side buttons are dropped there.

📄 Motivation and Context

Side buttons are the usual way to go back/forward in apps with history (browsers, file managers, docs viewers). On Tao they never reached Compose correctly:

• Windows / Linux: every extra button arrived as the same code, so Forward was indistinguishable from Back.
• macOS: all extra buttons were reported as Middle.

🧪 How Has This Been Tested?

On Linux (x64):

• cargo check of the native crate passes.
• The Linux natives rebuild through buildNativeLinux.
• :decorated-window-tao:test --tests '*TaoMouseButtonWireDriftTest*' passes.
• :decorated-window-tao:detekt and ktlintCheck pass.
• apiDump has been regenerated.
• Manual check with a real mouse's side buttons on Linux

Not yet tested:

• macOS and Windows native builds (the macOS change uses NSEvent::buttonNumber() from objc2-app-kit)
• Manual check with a real mouse's side buttons on Windows and macOS

📦 Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

⚠️ TaoMouseButton.OTHER changes from 3 to 5. It's a const val, so code compiled against the old value inlines 3 (now BACK) until it is recompiled.

✅ Checklist

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.

[kdroidFilter]

Can you target the nucleus 2.6 branch? Thank you very much!

[skyecodes]

Rebased onto nucleus-2.6 and changed the target branch.

[kdroidFilter]

thank you very much, you will be able to test it soon in the dev version 2.6.0-dev-202609251324

[skyecodes]

thank you very much, you will be able to test it soon in the dev version 2.6.0-dev-202609251324

Thanks for the dev release! I tested it on my application on Linux & Windows and it works fine 👍 I don't have a macOS machine so I couldn't test it on macOS unfortunately.