- Extract handleStreamingResponse into focused helper methods:
  - logStreamingRequest, makeStreamingRequest
  - readStream, processLines
  - hasBalancedBraces, tryParseAndProcess
  - accumulateContent, logParseError, buildStreamResult
- Introduce StreamState interface to pass state between methods
- Add node:stream/web import for ReadableStreamDefaultReader type
- Add 16 tests covering streaming, non-streaming, and error paths

- Extract resolveToolConfigured() for tool installation retry logic
- Extract buildScopeOptions() for scope selection options
- Extract configureTool() for tool-specific configuration
- Extract buildNextSteps() for next steps message generation
- Reorder functions to satisfy perfectionist/sort-modules
- All 45 existing tests pass

- Extract resolveApiKey() for API key resolution logic
- Extract resolveApiKeyFromId() for API key ID → key rotation
- Extract resolveApiKeyForList() for list command key resolution
- Extract resolveInputMessage() for stdin + argument combining
- Extract verifyAuthentication() for auth check
- Extract buildCompletionOptions() for options construction
- Extract runSingleShotChat() for non-interactive chat
- Extract runInteractiveChat() with createAskQuestion() for interactive mode
- Extract runInteractiveStreaming() and runInteractiveNonStreaming()
- Extract handleStreamingCompletion() and handleNonStreamingCompletion()
- Extract displayResponse() and displayModels() for output formatting
- Reorder functions alphabetically per perfectionist/sort-modules

…xity to ≤15

- Extract logCompletionOptions() for debug logging
- Extract formatCompletionError() and formatListModelsError()
- All 16 tests pass

- Extract resolveDefaultApiKey() for default API key resolution logic
- Simplify early returns for env var and command-line API keys

- Extract classifyRefreshError() to determine error handling action
- Extract storeNewTokens() for token persistence logic
- Introduce RefreshErrorAction interface for structured error classification
- All 12 existing tests pass

- Extract handleUndecodableJwt() for JWT decode failure path
- Extract handleHasSeat() for subscription seat flow
- Extract handleNoSeat() for no-subscription API key flow
- Extract createAndSyncApiKey() for shared API key creation logic
- All 40 existing tests pass