Feature request: python3 command support

Use Case

Python scripts are frequently executed inline (heredocs) or directly during AI-assisted development sessions. The output from Python scripts — tracebacks, print statements, data dumps — can be verbose and consume unnecessary context tokens.

Statistics (from rtk discover)

• ~570 python3 commands in 30 days (single user)
• ~420 heredoc invocations (python3 << 'EOF' ... EOF)
• ~150 direct script executions (python3 script.py)

Proposed Behavior

rtk python3 could:

• Compress long tracebacks (show only the relevant frames)
• Truncate large data output (e.g., list/dict dumps)
• Deduplicate repeated log lines (same as RTK already does for other commands)

Impact

Second most frequent unhandled command category in rtk discover output.