Warn when routing rules may not describe live routing

[cursor]

Surfaces warnings from GET .../routing-rules when a vtctld schema mutation is in progress.

• Human output prints each warning to stderr as Warning: ....
• JSON output preserves the API warnings array.

Tested: go test ./internal/cmd/branch/ ./internal/planetscale/, plus a local pscale branch routing-rules get against an API with a simulated mutation (stderr warning and JSON warnings both shown).

  

[cursor]

Screenshots of pscale branch routing-rules get against an API with a simulated in-progress vtctld schema mutation.

Human output (warning on stderr, rules still returned):

JSON output (warnings array with code schema_mutation_in_progress):

View PR

  

_{Sent by Cursor Automation: bugfix(vitess): author pull requests}