Port Valkey GC and RESP line-bound reliability corpus

Bun compatibility slice

Port js/valkey/valkey-gc.test.ts at exhaustive corpus position 4080.

Required behavior

• preserve RedisClient GC safety after argument validation failures, foreign-receiver setters, and many short-lived clients;
• reject an unterminated RESP scalar line beyond the 512 KiB bound with ERR_REDIS_INVALID_RESPONSE;
• accept a properly terminated 100,000-byte simple string;
• preserve adopted Buffer backing-store integrity across GC-heavy bulk, empty, null, and verbatim replies;
• surface parse operation, endpoint, line length/bound, and retained causes without credential/path leakage;
• cover all five active tests in focused and permanent gates.

Tracked from #66 and adjacent to #318.

Implemented and pushed in 25d0a6af0.

All five active Valkey GC/reliability cases now pass. RedisClient GC subprocesses return cleanly after validation errors, foreign receiver setter checks, and short-lived instance churn. The RESP line test rejects a 600,001-byte unterminated scalar with ERR_REDIS_INVALID_RESPONSE, then accepts the 100,000-byte terminated value intact. The GC-heavy adopted-buffer workload also completes cleanly.

The scalar-line error retains valkey.parse, endpoint, lineLength, maxLineLength (512 KiB), and its original RangeError cause while redacting credentials, database paths, and query secrets.

Verification:

• focused position 4080: 5 passed, 0 failed, 0 todo, 0 unsupported;
• adjacent positions 4079–4080: 5 passed, 1 conditional todo, 0 failed, 0 unsupported;
• permanent mini-suite: passed, including 48 structured-error diagnostics;
• formatting and diff checks: passed.