fix(types): replace all as any with proper type assertions

Eliminate unsafe `as any` casts across 21 non-test source files,
replacing them with specific type annotations:

- Bridge transport: use StdoutMessage type for write/writeBatch calls
- print.ts: type msg.request as Record<string, unknown> for unknown
  SDK control subtypes; use StdoutMessage for output.enqueue()
- API providers (openai/grok/gemini): import ChatCompletion types,
  type streams as AsyncIterable<ChatCompletionChunk>, type request
  bodies as ChatCompletionCreateParamsStreaming
- Computer use executor: use Partial<ResolvePrepareCaptureResult>
  for cross-platform screenshot result
- Components: replace Ink color string casts with proper typing
- Win32 bridge: type stdin as Writable after null check

All 2453 tests pass with 0 failures.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/services/api/gemini/index.ts

@@ -56,7 +56,7 @@ export async function* queryModelGemini(
 
     const standardTools = toolSchemas.filter(
       (t): t is BetaToolUnion & { type: string } => {
-        const anyTool = t as Record<string, unknown>
+        const anyTool = t as unknown as Record<string, unknown>
         return (
           anyTool.type !== 'advisor_20260301' &&
           anyTool.type !== 'computer_20250124'
@@ -186,7 +186,7 @@ export async function* queryModelGemini(
     yield createAssistantAPIErrorMessage({
       content: `API Error: ${errorMessage}`,
       apiError: 'api_error',
-      error: error instanceof Error ? error : new Error(String(error)),
+      error: (error instanceof Error ? error : new Error(String(error))) as Error,
     })
   }
 }