Treat ChatGPT hc plan as Enterprise

[arnavdugar-openai]

Motivation

• Cloud requirements fetching only ran for Business or Enterprise accounts, but some ID tokens report chatgpt_plan_type: "hc", which should be treated as an enterprise-equivalent plan.

Description

• Map raw plan string "hc" to KnownPlan::Enterprise in PlanType::from_raw_value by treating "enterprise" | "hc" as Enterprise in login/src/token_data.rs.
• Add a unit test in login/src/token_data_tests.rs asserting a JWT with chatgpt_plan_type: "hc" parses as Enterprise and is considered a workspace account.
• Add a unit test in cloud-requirements/src/lib.rs verifying hc accounts are eligible to fetch cloud requirements (treated like Enterprise).
• Run formatting (just fmt) after changes.

Testing

• Ran just fmt (succeeded).
• Ran cargo test -p codex-login --lib id_token_info_parses_hc_plan_as_enterprise (passed).
• Ran cargo test -p codex-cloud-requirements --lib fetch_cloud_requirements_allows_hc_plan_as_enterprise (passed) and cargo test -p codex-cloud-requirements (all tests passed).
• Ran just argument-comment-lint-from-source (required installing cargo-dylint/dylint-link and the nightly toolchain as part of the run).
• Note: a full cargo test -p codex-login run showed one unrelated, environment-dependent test failure (auth::default_client::tests::test_create_client_sets_default_headers) that is not caused by these changes; the targeted login unit added here passes.

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Codex Task

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