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/utils/streamlinedTransform.ts

@@ -137,13 +137,14 @@ export function createStreamlinedTransformer(): (
   ): StdoutMessage | null {
     switch (message.type) {
       case 'assistant': {
-        const content = message.message.content
+        const messageContent = (message as SDKAssistantMessage).message
+        const content = messageContent?.content
         const text = Array.isArray(content)
           ? extractTextContent(content, '\n').trim()
           : ''
 
         // Accumulate tool counts from this message
-        accumulateToolUses(message, cumulativeCounts)
+        accumulateToolUses(message as SDKAssistantMessage, cumulativeCounts)
 
         if (text.length > 0) {
           // Text message: emit text only, reset counts