[BUG] --print mode returns empty output in v2.1.83 (regression from v2.1.81)

Bug Description

claude --print mode returns empty output in v2.1.83, despite the API generating output tokens. This is a regression — v2.1.81 works correctly.

Reproduction Steps

# v2.1.83 - empty output
claude --print "say hello"
# (empty)

# v2.1.83 - JSON mode shows tokens generated but result is empty
claude --print --output-format json "say hello"
# {"type":"result","result":"","output_tokens":23,...}

# v2.1.81 - works correctly
~/.local/share/claude/versions/2.1.81 --print "say hello"
# Hello! How can I help you today?

Key Observations

• output_tokens are generated (5-40 tokens depending on prompt), confirming the model IS responding
• result field in JSON output is always "" (empty string)
• stop_reason is "end_turn" (normal completion)
• Affects both text and JSON output formats
• Happens with all models (opus, sonnet)
• Happens with --system-prompt override (not caused by CLAUDE.md)
• Happens with DISABLE_OMC=1 and minimal environment
• Tested with nohup + file redirection to rule out terminal/nesting issues

Environment

• Broken version: 2.1.83 (installed 2026-03-25 15:46)
• Working version: 2.1.81 (installed 2026-03-23)
• Platform: macOS Darwin 25.2.0
• Auth: OAuth (re-login did not fix the issue)

Impact

This breaks any automation relying on claude --print for non-interactive usage (CI/CD pipelines, daemon processes, scripts).

Workaround

Pin to v2.1.81 binary: ~/.local/share/claude/versions/2.1.81