Instrument CLI entrypoints to create root spans for user-initiated operations

[psschwei]

Description:
Instrument CLI entrypoints to create root spans for user-initiated operations.

Detailed Requirements:

1. Create root span for each CLI command:
   • cli.serve - Serve command execution
   • cli.decompose - Decomposition command
   • cli.eval - Evaluation command
   • cli.alora - ALoRA commands
2. Add command-specific attributes:
   • cli.command - Command name
   • cli.args - Sanitized argument summary (no secrets)
3. Create reusable decorator or context manager for CLI tracing
4. Ensure spans are properly closed even on exceptions

Files to Modify:

• cli/m.py - Add tracing infrastructure
• cli/serve/app.py - Instrument serve command
• cli/decompose/decompose.py - Instrument decompose
• cli/eval/commands.py - Instrument eval commands
• cli/alora/commands.py - Instrument alora commands

Example Usage:

@app.command()
def serve(port: int = 8000):
    with trace_application("cli.serve", command="serve", port=port):
        # ... serve implementation

Acceptance Criteria:

• Root span created for each CLI command
• Command name and relevant args captured
• Spans closed on success and exception
• CLI remains functional when tracing disabled

[ajbozarth]

Closing as part of the tracing epic (#444) re-plan. This sub-issue predates the plugin/hooks pattern (PR #653) and the GenerationMetadata partition (PR #908); its spec has drifted.

Replacement: #1052 — CLI root spans, refreshed for the current CLI layout.

See #444 for the full refreshed plan.