Display workspace usage limit error copy from response header

[dhruvgupta-oai]

Why

openai/openai#947613 adds X-Codex-Rate-Limit-Reached-Type for Codex workspace credit-depletion and spend-cap responses. The CLI currently reads the adjacent promo header but otherwise renders generic usage-limit copy, so those responses do not explain the workspace-specific action the user needs to take.

Backend dependency: https://github.com/openai/openai/pull/947613

What Changed

• Parse X-Codex-Rate-Limit-Reached-Type in the usage-limit error handling path alongside x-codex-promo-message.
• Keep the header value parsing with the shared RateLimitReachedType enum.
• Carry the parsed type on UsageLimitReachedError and render client-owned copy for the four workspace owner/member credit and spend-cap values.
• Preserve existing promo and plan-based text for absent, generic, or unknown header values.
• Keep the existing TUI workspace-owner nudge state path unchanged; the response header only selects the displayed error string.
• Add focused display coverage for all specific type values and the generic fallback case.

Test Plan

• Added usage_limit_reached_error_formats_rate_limit_reached_types coverage.
• Not run manually, per request; CI runs validation on the pushed commit.

[fcoury-oai]

Reviewed only the code, didn't run any smoke tests.

The code looks good, but added 2 nitpicks and one request for additional test coverage, but not blockers.