Add durable profile acceptance fixtures

[IlyaasK]

Summary

• add durable profile create/delete methods to the provider-local Kernel client
• preserve explicit project scope and disable SDK retries for both mutations
• add guarded, deadline-bound cleanup for acceptance profile fixtures
• test cleanup gating, default and explicit scope, 404 handling, and deletion errors
• keep profile archive download outside the provider-local client surface

Why

The existing kernel_profile data source needs a real durable fixture for live acceptance coverage. This PR adds only the setup and cleanup boundary; it does not add a Terraform profile resource or change provider behavior.

Scope

internal/kernelclient continues to expose durable operations only. This PR does not expose profile archive download, browser-session profile saves, or any runtime operation.

The profile data-source acceptance scenario and workflow entry remain in the next stacked PR.

Tests

• go test -short -timeout=2m ./internal/acctest ./internal/kernelclient
• go test -race -short -timeout=2m ./internal/acctest ./internal/kernelclient
• go test -short -timeout=2m ./...
• go vet ./...
• go mod verify
• go mod tidy -diff
• gofmt -l cmd internal
• terraform fmt -check -recursive examples
• bash scripts/check-docs.sh
• bash scripts/check-markdown-links.sh

No live API call is part of this fixture-plumbing PR.

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Note

Low Risk
Test and internal client helper changes only; no provider resources or production code paths.

Overview
Adds acceptance-test plumbing so durable Kernel profiles can be created and torn down for upcoming live coverage (e.g. kernel_profile), without changing Terraform provider behavior.

internal/kernelclient gains CreateProfile and DeleteProfile, using explicit project scope and disabled SDK retries on mutations (same pattern as other durable writes). Client tests cover those endpoints and assert DownloadProfile is not on the Clients surface.

internal/acctest adds CleanupProfile, mirroring existing project/browser-pool cleanup: gated on acceptance env + API key, optional default project resolution, deadline-bound delete, and 404 treated as already clean. New unit tests exercise gating, scope, errors, and cleanup registration.

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