feat: add gemini-3-flash support and comprehensive lint fixes

[Dhinesh kumaran S (Dhineshkumaran)]

• Add gemini-3-flash-preview and gemini-2.5-* context limits to ContextUsageIndicator.
• Refactor WorkspacePicker to move selectWorkspaceFolder to lib/workspace-utils.ts to resolve React Fast Refresh warnings.
• Fix missing explicit return types in ChatContainer, ModelSwitcher, ApiKeyDialog, MessageBubble, hreads.ts, and various Tab components.
• Fix unused variable warnings in storage.ts and hread-context.tsx.
• Fix import errors and ensure clean linting state across the renderer and main process.

Description

This PR adds support for gemini-3-flash and other recent Gemini models to the context awareness system, and performs a comprehensive linting pass to improve code quality and type safety across the application.

Detailed Changes

Feature: Gemini 3 Support

• ContextUsageIndicator: Added explicit context window configurations for gemini-3-flash-preview and gemini-2.5-flash-lite (and their pro variants), ensuring accurate token usage tracking for these new models.

Refactoring & Performance

• WorkspacePicker: Refactored logic to address a React Fast Refresh warning (react-refresh/only-export-components). The selectWorkspaceFolder helper utility was moved to a separate file: src/renderer/src/lib/workspace-utils.ts.
• ModelSwitcher: Optimized component by removing unnecessary useEffect calls that were causing cascading renders and replaced them with derived state.

Lint Fixes (ESLint Cleanup)

Addressed extensive explicit-function-return-type and no-unused-vars lint errors across the codebase:

• Chat Components: Added return types to ChatContainer, ModelSwitcher, ApiKeyDialog, MessageBubble, and ToolCallRenderer.
• Tab Components: Added return types to ImageViewer, MediaViewer, PDFViewer, BinaryFileViewer, and TabBar.
• Backend/IPC: Fixed return types in threads.ts and resolved unused variables in storage.ts.
• Context: Cleaned up thread-context.tsx by properly handling unused variables and suppressing necessary Fast Refresh warnings for exported hooks.
• Config: Fixed lint errors in electron.vite.config.ts.

Related Issue

Fixes #36

Type of Change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update
• Refactoring (no functional changes)

Checklist

• I have read the Contributing Guide
• I have tested my changes locally
• My changes generate no new warnings
• Any dependent changes have been merged and published

Additional Notes

This fixes the lint error in #17 pull request. 👍

[Hunter Lovell (hntrl)]

Thanks for the PR!

[Hunter Lovell (hntrl)]

Merging with a failing build -- won't release until we merge build + format fixes across the whole stack.

[Dhinesh kumaran S (Dhineshkumaran)]

Thanks for the update!
Happy to help with the build or formatting fixes if needed — let me know 👍