fix: write execution file when SDK throws

[Jerry2003826]

Fixes #1226

Summary

• Persist the SDK message log before rethrowing SDK execution errors.
• Reuse the same execution-file writer on success and error paths.
• Add regression coverage for SDK errors after partial output.

Root Cause

runClaudeWithSdk only wrote EXECUTION_FILE after the SDK async iterator completed. When query() threw, for example with error_max_turns, the catch path rethrew before writing the partial message log.

Validation

• bun test test/run-claude-sdk.test.ts
• bun test
• bun run typecheck
• bunx prettier --check src/run-claude-sdk.ts test/run-claude-sdk.test.ts

Note: full bun run format:check on this Windows checkout reports pre-existing formatting/line-ending issues across unrelated files, so I verified the changed files with Prettier directly.