fix(terminal): skip WebGL renderer on software-only GPU

[gregpriday]

Summary

• Adds a GPU detection check before attaching @xterm/addon-webgl to terminals. When Chromium reports WebGL as software_only (CPU-emulated via llvmpipe or ANGLE fallback), WebGL attachment is skipped entirely and terminals fall back to the DOM renderer automatically.
• Exposes GPU WebGL status from the main process via a new IPC handler (app/state) so the renderer can read it at startup through stateHydration.
• Extracts GPU detection logic into electron/utils/gpuDetection.ts to keep the IPC handler thin and the helper independently testable.

Resolves #3280

Changes

• electron/utils/gpuDetection.ts — new helper that reads app.getGPUFeatureStatus().webgl2 and returns whether hardware WebGL is available
• electron/ipc/handlers/app/state.ts — surfaces gpuWebGLAvailable flag in the app state IPC response
• shared/types/ipc/app.ts — adds gpuWebGLAvailable: boolean to the AppState type
• src/utils/stateHydration.ts — hydrates the GPU flag into a module-level export consumed by TerminalWebGLManager
• src/services/terminal/TerminalWebGLManager.ts — guards ensureContext() with the hydrated GPU flag; logs a clear message when WebGL is skipped
• src/services/terminal/TerminalInstanceService.ts — calls hydrateGpuState() at startup before any terminal is created
• Tests covering GPU detection, state hydration, and the WebGL skip path

Testing

• Unit tests pass for all new and modified files (TerminalWebGLManager.test.ts, stateHydration.test.ts, app.gpuDetection.test.ts)
• npm run check passes cleanly (typecheck, lint, format)
• The existing CANOPY_DISABLE_WEBGL=1 env override continues to work alongside the new runtime check

[gregpriday]

Review status: Ready

• Cross-PR note: File overlap with fix(terminal): reduce WebGL context pool to leave headroom for Chromium limit #3358 (TerminalWebGLManager.ts) — different sections, no conflict. Merge fix(terminal): reduce WebGL context pool to leave headroom for Chromium limit #3358 first.