[WRONG BRANCH] fix(server): strip passthrough redirect Location to prevent credential replay

[luvs01]

Motivation

• Forward-mode passthrough relayed upstream 3xx responses with their Location header, which can cause clients that follow redirects to replay request bodies and custom admission headers (including X-OpenCodex-API-Key) to attacker-controlled hosts. This is a high-severity data-plane credential exposure.

Description

• Drop Location from the passthrough header sanitizer by adding it to the DROP set in src/server/relay.ts so relayed responses never expose upstream redirect targets.
• Remove location from the compact passthrough allowlist in src/server/responses/compact.ts so buffered/compact responses also do not expose upstream Location.
• Update src/server/responses/core.ts to clarify the manual-redirect behavior and to use the sanitizer that no longer exposes Location.
• Add focused regression tests: adjust the passthrough 307 test in tests/server-auth.test.ts to assert the Location is stripped, and add a compact-path test in tests/errors-adapter-failure.test.ts asserting compact responses do not expose Location.

Testing

• Ran targeted tests: node_modules/.bin/bun test tests/server-auth.test.ts -t "passthrough pool send strips a 307" and node_modules/.bin/bun test tests/errors-adapter-failure.test.ts, both passed.
• Ran typecheck: node_modules/.bin/bun run typecheck, which passed.
• Ran privacy scan: node_modules/.bin/bun run privacy:scan, which passed.
• Ran the full test script in this environment; the broad integration suite encountered unrelated environment-dependent failures (external package registry HTTP 403 and Docker/root-specific assertions), so the full-suite run is inconclusive in this environment but the focused regression tests and static checks above passed.

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Review details

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📥 Commits

Reviewing files that changed from the base of the PR and between 2468502 and bcb55d3.

📒 Files selected for processing (5)

• src/server/relay.ts
• src/server/responses/compact.ts
• src/server/responses/core.ts
• tests/errors-adapter-failure.test.ts
• tests/server-auth.test.ts

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[github-actions]

⏳ DRAFT

• wrong target branch (main); retarget to dev.

What to do

• Retarget this PR to dev — all contributions go to dev.

Its title has been prefixed with [WRONG BRANCH].
This pull request was already a draft. Its draft status will be preserved after every issue above is resolved.

[github-actions]

✅ Deterministic PR hygiene checks passed.