Show a CLI warning when using autocreated fleets

[r4victor]

Part of #3059

The PR shows a CLI warning when an autocreated fleet is used on run apply. Also includes fleet to run API responses to be able to get run's fleet.

[peterschmidt85]

@r4victor Do you want to merge it before the release?

[r4victor]

Yes, the sooner the better

[peterschmidt85]

When running older CLI with new server:

dstack fleet
Traceback (most recent call last):
  File "/Users/cheptsov/.local/bin/dstack", line 10, in <module>
    sys.exit(main())
             ~~~~^^
  File "/Users/cheptsov/.local/share/uv/tools/dstack/lib/python3.13/site-packages/dstack/_internal/cli/main.py", line 91, in main
    args.func(args)
    ~~~~~~~~~^^^^^^
  File "/Users/cheptsov/.local/share/uv/tools/dstack/lib/python3.13/site-packages/dstack/_internal/cli/commands/fleet.py", line 68, in _command
    args.subfunc(args)
    ~~~~~~~~~~~~^^^^^^
  File "/Users/cheptsov/.local/share/uv/tools/dstack/lib/python3.13/site-packages/dstack/_internal/cli/commands/fleet.py", line 71, in _list
    fleets = self.api.client.fleets.list(self.api.project)
  File "/Users/cheptsov/.local/share/uv/tools/dstack/lib/python3.13/site-packages/dstack/api/server/_fleets.py", line 25, in list
    return parse_obj_as(List[Fleet.__response__], resp.json())
  File "pydantic/tools.py", line 38, in pydantic.tools.parse_obj_as
  File "pydantic/main.py", line 347, in pydantic.main.BaseModel.__init__
pydantic.error_wrappers.ValidationError: 2 validation errors for ParsingModel[List[dstack._internal.core.models.fleets.FleetResponse]]
__root__ -> 0 -> spec -> configuration -> nodes -> target
  extra fields not permitted (type=value_error.extra)
__root__ -> 0 -> spec -> __root__
  Missing profile or configuration (type=value_error)

[peterschmidt85]

I tried to run a dev environment (no existing fleets) but it didn't show me any warnings related to fleet creation.

[r4victor]

The warning is shown after the provisioning table

[peterschmidt85]

The warning is shown after the provisioning table

I suppose it's difficult to show it before Submit the run cursor? [y/n], right? If so, then it's OK.

Also, if possible please shorten the warning to

No existing fleet matched, so the run created a new fleet <run name>. Future dstack versions won’t create fleets automatically. Create a fleet explicitly: https://dstack.ai/docs/concepts/fleets/

[r4victor]

When running older CLI with new server:

dstack fleet
Traceback (most recent call last):
  File "/Users/cheptsov/.local/bin/dstack", line 10, in <module>
    sys.exit(main())
             ~~~~^^
  File "/Users/cheptsov/.local/share/uv/tools/dstack/lib/python3.13/site-packages/dstack/_internal/cli/main.py", line 91, in main
    args.func(args)
    ~~~~~~~~~^^^^^^
  File "/Users/cheptsov/.local/share/uv/tools/dstack/lib/python3.13/site-packages/dstack/_internal/cli/commands/fleet.py", line 68, in _command
    args.subfunc(args)
    ~~~~~~~~~~~~^^^^^^
  File "/Users/cheptsov/.local/share/uv/tools/dstack/lib/python3.13/site-packages/dstack/_internal/cli/commands/fleet.py", line 71, in _list
    fleets = self.api.client.fleets.list(self.api.project)
  File "/Users/cheptsov/.local/share/uv/tools/dstack/lib/python3.13/site-packages/dstack/api/server/_fleets.py", line 25, in list
    return parse_obj_as(List[Fleet.__response__], resp.json())
  File "pydantic/tools.py", line 38, in pydantic.tools.parse_obj_as
  File "pydantic/main.py", line 347, in pydantic.main.BaseModel.__init__
pydantic.error_wrappers.ValidationError: 2 validation errors for ParsingModel[List[dstack._internal.core.models.fleets.FleetResponse]]
__root__ -> 0 -> spec -> configuration -> nodes -> target
  extra fields not permitted (type=value_error.extra)
__root__ -> 0 -> spec -> __root__
  Missing profile or configuration (type=value_error)

Turned out pydantic-duality functionality does not work for some of our models due to overridden Config leading to this. See #3066