feat: add Atlas Cloud provider

[binyangzhu000-sudo]

Summary

• add Atlas Cloud as a built-in OpenAI-compatible provider alias
• discover ATLASCLOUD_API_KEY for automatic model selection and credential forwarding
• document inline and named-model configuration

Testing

• go test ./pkg/model/provider (focused alias and end-to-end provider tests)
• go test ./pkg/config ./pkg/runtime ./pkg/creator ./pkg/environment (focused provider/config tests)
• go run ./lint .
• golangci-lint v2.12.2 run
• go mod tidy --diff
• CI=true ./scripts/build.sh
• live Atlas Cloud Chat Completions smoke test (HTTP 200)

[aheritier]

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[Sayt-0]

Adding Atlas Cloud as a built-in alias follows the established pattern and the Go changes are complete and well tested. Three integration points are missing and the default model needs verification before merge.

#	Finding	File	Blocking
1	New docs page absent from the sidebar	docs/data/nav.yml	yes
2	Built-in alias table not updated	docs/concepts/models/index.md	yes
3	Provider list in schema description not updated	agent-schema.json	no
4	Default model qwen/qwen3.8-max unverifiable	pkg/config/auto.go (see inline)	yes
5	Front matter weight breaks alphabetical convention	docs/providers/atlascloud/index.md (see inline)	no

Ready-to-paste fixes for the files outside the diff:

1. docs/data/nav.yml, between the Anthropic and AWS Bedrock entries:

    - title: Atlas Cloud
      url: /providers/atlascloud/

2. docs/concepts/models/index.md, built-in alias table, after the OpenRouter row (matches the placement used in docs/providers/overview/index.md; adjust the description column if needed):

| Atlas Cloud         | `atlascloud`     | Qwen and other open models           | `ATLASCLOUD_API_KEY`                |

3. agent-schema.json, provider description, add atlascloud after openrouter in the alias enumeration:

... any built-in alias (requesty, openrouter, atlascloud, azure, xai, ...)

Process notes:

• The status/needs-signed-commits label is set; the commit must be signed before merge.
• The branch is 11 commits behind main. A rebase also picks up 95f3d1a, which fixes the pre-existing TestParseExamples gopher failures in pkg/config, unrelated to this PR but noisy in local runs.

[Sayt-0]

Provider pages use alphabetical-by-title weights in increments of 10 (Anthropic 20, AWS Bedrock 30, Baseten 40, ...). "Atlas Cloud" sorts between Anthropic and AWS Bedrock, so 235 places the page between OpenRouter and OVHcloud in weight-ordered listings.

Suggested change

	weight: 235
	weight: 25

[Sayt-0]

Can the existence of qwen/qwen3.8-max in the Atlas Cloud catalog be confirmed (catalog link or output of the live smoke test mentioned in the PR description)? Two concerns:

• This ID is the auto-selection default: if it is wrong, every user with only ATLASCLOUD_API_KEY set gets a broken first run.
• Neither an atlascloud provider nor any qwen3.8-max entry exists in pkg/modelsdev/snapshot.json, so capability lookup falls back to text-only with a warning. A "-max" model is also unusual for an open-model host (the -max line is API-only, not open weights), which is worth double-checking against the openModelHostProviders classification.

If the ID changes, the two examples in docs/providers/atlascloud/index.md (atlascloud/qwen/qwen3.8-max and model: qwen/qwen3.8-max) and the assertions in pkg/config/auto_test.go and pkg/model/provider/openai_alias_providers_test.go must be updated in sync.