Framework log lines written to stdout pollute model method output

Description

When running swamp model method run, framework-level log lines are written to stdout and intermixed with the model's own stdout output. This makes it impossible to pipe or redirect clean output from a model method without garbage lines at the top of the file.

Steps to Reproduce

1. Create a model that writes formatted output to stdout (e.g. markdown tables)
2. Run: swamp model method run my-model myMethod > report.md
3. Open report.md

Expected Behavior

report.md should contain only the model's stdout output — clean, parseable content.

Actual Behavior

The file contains 3+ framework log lines before the model output:

Found model "my-model" ("@org/my-model")
Evaluating expressions
Executing method "myMethod"

These are framework-level info logs that should be written to stderr, not stdout, so that stdout remains clean for programmatic use.

Workaround

The -q / --quiet flag suppresses these lines:

swamp model method run my-model myMethod -q > report.md

However, the default behavior should respect the Unix convention of keeping stdout for data and stderr for diagnostics.

Suggested Fix

The model method run command's framework-level log output should be written to stderr instead of stdout. This affects the log rendering layer — the structured log entries themselves are fine, they just need to target the correct output stream.