Display workspace usage limit error copy from response header (#24114)

## 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.

codex-rs/codex-api/src/rate_limits.rs

@@ -1,5 +1,6 @@
 use codex_protocol::account::PlanType;
 use codex_protocol::protocol::CreditsSnapshot;
+use codex_protocol::protocol::RateLimitReachedType;
 use codex_protocol::protocol::RateLimitSnapshot;
 use codex_protocol::protocol::RateLimitWindow;
 use http::HeaderMap;
@@ -178,6 +179,13 @@ pub fn parse_promo_message(headers: &HeaderMap) -> Option<String> {
         .map(std::string::ToString::to_string)
 }
 
+pub(crate) fn parse_rate_limit_reached_type(headers: &HeaderMap) -> Option<RateLimitReachedType> {
+    parse_header_str(headers, "x-codex-rate-limit-reached-type")?
+        .trim()
+        .parse()
+        .ok()
+}
+
 fn parse_rate_limit_window(
     headers: &HeaderMap,
     used_percent_header: &str,