Changes

Ports --override KEY=VALUE from the Python CLI. Overrides apply to the parsed YAML map before re-decode + validate, so path existence, type coercion, and semantic validate() rules all run. A reflection-based path check names the exact --override key and lists available fields on error.

Why

--override allows users to tweak a training configuration at launch time without editing the file and this allows for ease of use with sweep hyperparameters or scalable compute without having to maintain a forked configuration for each run.

Tests

unit tests:

• TestParseOverrides: parsing KEY=VALUE
• TestValidateOverridePaths: dotted-path validation against the schema
• TestLoadRunConfigWithOverrides: end-to-end through the loader: scalar coercion, multiple overrides, free-form env-var-as-string, auto-created intermediate maps, unknown-path rejection, semantic re-validation after override, type mismatch, malformed override.
• TestSubmitWorkload: the harness pattern being extended to prove overrides reach the actual POST body sent to /api/2.2/jobs/runs/submit, verified against the in-process testserver that records the request.
• TestSubmitWorkloadHonorsOverride: proves a --override actually changes what gets sent to the Jobs API on a real submit, not just during dry-run validation.

acceptance tests:

• successful override that logs the change and then validates
• an unknown field override that errors with an actionable message (see screenshots below)
• override that passes type checking but fails schema validation (so we know that validate() still runs and works properly)

Manual verification: