feat(vks): update_nodegroup disable_auto_scale sends autoScaleConfig:null

[vks-team]

Summary

Mirrors the greennode-cli update-nodegroup alignment onto the MCP update_nodegroup tool. The backend's autoScaleConfig is JsonNullable, but the tool's Optional[AutoScaleConfig]=None + model_dump(exclude_none=True) could only express two states — omit (keep) and object (set). Disabling autoscaling (send autoScaleConfig: null to delete the current config) was impossible.

Add a disable_auto_scale: bool sentinel to UpdateNodeGroupDto (mirroring the CLI's --disable-auto-scale). The handler rejects it together with an autoScaleConfig object (mutually exclusive), strips the sentinel from the payload, and sets an explicit autoScaleConfig: None so the wire body carries "autoScaleConfig": null.

State	Call	Wire body
keep	omit autoScaleConfig	field absent
disable	disable_auto_scale=true	"autoScaleConfig": null
set	autoScaleConfig={...}	"autoScaleConfig": {...}

Only one state needed work

The two other gaps the CLI fix closed are already handled by the pydantic models here — no code needed:

• Object missing minSize/maxSize → reject: AutoScaleConfig declares minSize: int = Field(...) + maxSize: int = Field(...) required, so pydantic rejects {}/partial objects at parse.
• upgradeConfig fills defaults 1/0: UpgradeConfig declares maxSurge=Field(1,...), maxUnavailable=Field(0,...) as defaults, so an empty UpgradeConfig() already sends {maxSurge:1, maxUnavailable:0}.

Only the disable state needed code.

Why a sentinel bool, not exclude_unset/JsonNullable

model_dump(exclude_unset=True) distinguishes "unset" from "provided as None", the pydantic-native 3-state path. But it requires the LLM caller to explicitly pass autoScaleConfig=None to disable — a fragile, undocumented argument contract. A sentinel bool is an unambiguous, self-documenting argument ("disable_auto_scale": true) that matches the CLI's UX. Cost: one extra field the handler strips — trivial.

Test plan

Four new tests in test_nodegroup_tools.py pin all three states plus the mutex:

Test	Verifies
disable_autoscale_sends_null	wire body is {"autoScaleConfig": None}, sentinel stripped, HTTP PUT made
disable_and_object_is_mutually_exclusive	mutex error returned, no HTTP call
omits_autoscale_when_unset	autoScaleConfig absent from wire (keep current) — pin
sends_autoscale_object	object present on wire — pin

Check	Result
uv run pytest tests/	281 passed
uv run ruff check .	all checks passed
uv run ruff format --check .	45 files already formatted

Ported from

greennode-cli PR #11 (update-nodegroup --disable-auto-scale + autoscale null + upgrade defaults). The fail-fast and upgrade-defaults parts were unnecessary here because pydantic's Field(...) required-fields and Field(default) already enforce them; only the disable state ported.