fix: incomplete toolbar back button customization

[WhiredPlanck]

Pull request

Issue tracker

Fixes will automatically close the related issues

Fixes # N/A

Feature

Describe features of this pull request

Code of conduct

• CONTRIBUTING

Code style

• make sytle-lint
• Conventional Commits

Build pass

• make debug

Manually test

• Done

Code Review

1. No wildcards import
2. Manual build and test pass
3. GitHub Action CI pass
4. At least one contributor review and approve
5. Merged clean without conflicts
6. PR will be merged by rebase upstream base

Daily build

Login and download artifact at https://github.com/osfans/trime/actions

Additional Info

[Copilot]

Pull request overview

This PR aims to make the toolbar/tab-bar “back” button styling follow theme customization more consistently by centralizing back-button rendering in shared UI components instead of per-window implementations.

Changes:

• Removes the clipboard window’s custom back button and relies on the shared tab bar back button instead.
• Updates TabUi to build its back button using theme toolbar configuration (via backStyle) when possible.
• Tightens ToolButton style handling (non-null style, simplified style-update checks) and adjusts toolbar button click callback types.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
app/src/main/java/com/osfans/trime/ime/clipboard/ClipboardWindow.kt	Removes clipboard-specific back wiring and lets the shared tab bar handle navigation.
app/src/main/java/com/osfans/trime/ime/clipboard/ClipboardTitleUi.kt	Removes the embedded back button from the clipboard title layout.
app/src/main/java/com/osfans/trime/ime/bar/ui/ToolButton.kt	Makes style handling stricter (non-null) and simplifies style-update detection.
app/src/main/java/com/osfans/trime/ime/bar/ui/TabUi.kt	Adds themed back-button construction intended to respect tool_bar.back_style.
app/src/main/java/com/osfans/trime/ime/bar/ui/ButtonsBarUi.kt	Changes the click callback type and refactors click/long-click setup.
app/src/main/java/com/osfans/trime/ime/bar/ui/AlwaysUi.kt	Changes click callback type and refactors button creation; currently introduces a state-switch crash risk.

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