fix(linux): avoid Wayland EGL startup failure

[tuannx]

Summary

• detect Wayland before Tauri/WebKitGTK initialization
• select WebKitGTK's DMA-BUF fallback when no user renderer override is present, avoiding the EGL_BAD_PARAMETER startup abort reported on Arch/Plasma Wayland
• preserve explicit WEBKIT_DISABLE_DMABUF_RENDERER choices and provide THINKUTILS_SKIP_WAYLAND_WORKAROUND=1 as an opt-out
• document the behavior and cover Wayland, X11, override, and opt-out decisions

Closes #12.

Why this is early startup code

The renderer environment must be set before thinkutils_lib::run() initializes Tauri and creates the WebKitGTK webview. Applying it in setup hooks would be too late for the failing EGL display initialization.

Validation

Executed in a clean Debian 12 ARM64 Linux container with the same WebKitGTK/GTK packages required by CI:

• cargo fmt --all -- --check
• cargo clippy --all-targets -- -D warnings
• cargo test — 136 passed, 0 failed, including 2 new Linux Wayland decision tests
• git diff --check

I could not reproduce a physical Plasma/Wayland compositor inside the headless container, so the PR remains draft for a reporter/maintainer smoke test on the affected desktop.

[tuannx]

Arcade Agent architecture review (fresh cache)

I ran an optional Rust architecture pass against this branch with Arcade Agent's in-review Rust parser (lemduc/arcade-agent#18). The first repo-root attempt correctly reported no directly rooted Rust sources, so I reran against src-tauri/ from a clean cache; generated cache data was removed afterward.

General result:

• parsed 325 Rust entities and 425 dependency edges into 17 recovered components
• Balanced Architecture Score: 0.9058
• Principle Alignment Score: 0.8868
• strongest signals: Acyclic Dependencies 1.0, Responsibility Focus 1.0, Interface Segregation 1.0, Boundary Clarity 0.9779
• main improvement signals: Dependency Distribution 0.4706, Component Balance 0.5747, Hub Balance 0.75
• no architecture smells detected

Proposal: once Rust parsing is merged and shipped in an Arcade Agent release, add a non-blocking PR report scoped to src-tauri/. That scope matters here because the repository root is frontend-first and the current analyzer discovers no Rust files from that root. A non-blocking rollout would let maintainers observe score stability before considering regression thresholds.

This PR does not add an analyzer dependency or modify CI policy.