Go SDK: models.gen.go is behind the supervisor schema snapshot

[henry3260]

go-sdk/pkg/execution/genmodels/models.gen.go is generated from the supervisor wire-schema
snapshot at task-sdk/src/airflow/sdk/execution_time/schema/schema.json, and it is behind it.

The snapshot last moved in #73224 and #73027; the models were last regenerated in #73531,
before both. Running just generate-models on current main adds two fields:

MultiTeam   bool        `msgpack:"multi_team,omitempty"`
RetryReason interface{} `msgpack:"retry_reason,omitempty"`

Nothing failed, because msgpack drops a field the struct does not declare — so the supervisor
sends these and the Go SDK cannot see them.

Nothing regenerates or verifies the file, which is why the drift went unnoticed across two PRs.
The Go SDK's Dag specs got a check for exactly this in #73936
(scripts/ci/prek/check_go_sdk_spec_drift.py): regenerate, then ask Git whether the committed
file changed.

To do

• Regenerate models.gen.go and commit it.
• Extend the drift check to cover it, so a snapshot change that never reaches Go fails CI.

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Drafted-by: Claude Code (Opus 5) (no human review before posting)