Summary

• Root cause: When a cached terminal is reattached to a DOM container (tab switch, pane focus) or resized, attachToContainer in v1-terminal-cache.ts calls xterm.refresh() but never clears the WebGL texture atlas. Stale glyph textures from the previous rendering context persist, causing garbled text and background terminal content ghosting into the chat view on macOS.
• Fix: Expose clearTextureAtlas() from the xterm WebglAddon via createTerminalInWrapper() in helpers.ts, store it in CachedTerminal, and call it in attachToContainer before refresh() and in the ResizeObserver callback when dimensions change. This forces the WebGL renderer to rebuild its glyph texture from scratch on every reattach/resize, eliminating stale rendering artifacts.
• Test: Added v1-terminal-cache.test.ts with 5 tests that model the attach/resize logic and verify clearTextureAtlas is called at the right times (before refresh on reattach, on resize when dimensions change, not on no-op resize).

Test plan

• bun test apps/desktop/src/renderer/screens/main/components/WorkspaceView/ContentView/TabsContent/Terminal/ — all 73 tests pass (including 5 new)
• bun run lint:fix — passes clean
• Manual verification on macOS: open multiple terminal panes, switch tabs, resize window — no garbled text or ghosting

Closes #3504

Summary by cubic

Fixes issue #3504 by clearing the xterm WebGL texture atlas when a cached terminal is reattached or resized. This removes stale glyphs and prevents garbled text and ghosting on macOS.

• Bug Fixes
  • Expose clearTextureAtlas from WebglAddon via createTerminalInWrapper, store on CachedTerminal.
  • Call clearTextureAtlas() in attachToContainer before refresh() and on ResizeObserver dimension changes.
  • Add 5 tests covering reattach, resize, call order, and no-op resize.

^{Written for commit 09b38ac. Summary will update on new commits.}