refactor(proxy): return remaining header from rateLimitSignal to eliminate duplicate read

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X-Ratelimit-Remaining was read twice in the same call chain: once inside rateLimitSignal and again in its caller injectRetryAfterIfRateLimited. This creates a latent inconsistency risk if the header name is ever changed in one place but not the other.

Changes

• rateLimitSignal: Extended return signature from (bool, string) to (bool, string, string) — now returns (isRateLimited, resetHeader, remaining)
• injectRetryAfterIfRateLimited: Removed redundant resp.Header.Get("X-Ratelimit-Remaining") call; uses remaining from rateLimitSignal directly
• Tracing call site: Updated to discard the new third return value with _
• Tests: Added assertions on the remaining return value in all three TestRateLimitSignal subtests

// Before
func rateLimitSignal(resp *http.Response) (bool, string) { ... }
// injectRetryAfterIfRateLimited called rateLimitSignal then read the header again

// After
func rateLimitSignal(resp *http.Response) (bool, string, string) {
    remaining := resp.Header.Get("X-Ratelimit-Remaining")
    return is429 || remaining == "0", resp.Header.Get("X-Ratelimit-Reset"), remaining
}

[Copilot]

Pull request overview

Refactors the proxy rate-limit detection path to avoid reading X-Ratelimit-Remaining twice by returning the parsed “remaining” value from rateLimitSignal and reusing it in injectRetryAfterIfRateLimited. This reduces duplication and keeps the rate-limit header handling consistent within the call chain.

Changes:

• Extended rateLimitSignal to return (isRateLimited, resetHeader, remaining) and updated call sites accordingly.
• Removed redundant resp.Header.Get("X-Ratelimit-Remaining") in injectRetryAfterIfRateLimited and reused the returned remaining.
• Updated unit tests to assert the new remaining return value across all TestRateLimitSignal subtests.

Show a summary per file

File	Description
internal/proxy/handler.go	Updates rateLimitSignal signature and eliminates the duplicate header read in injectRetryAfterIfRateLimited; updates tracing call site to ignore the new return value.
internal/proxy/rate_limit_test.go	Updates tests to capture and assert the new remaining return value from rateLimitSignal.

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• Files reviewed: 2/2 changed files
• Comments generated: 0
• Review effort level: Low