cargo-mono: remove sparse index prefetch timeout

[kdy1]

Summary

• remove the explicit 15s reqwest timeout from cargo-mono sparse index prefetch during publish
• keep existing prefetch concurrency, rate-limit retry, and already-published skip behavior unchanged
• document that crates.io sparse-index prefetch relies on the HTTP client's default timeout behavior

Why

cargo-mono publish prefetch could fail early on slower registry responses because it enforced a separate client-side timeout for sparse index lookups. Removing that override avoids premature lookup failures without changing the existing publish retry and backoff behavior.

Impact

• sparse-index prefetch no longer imposes its own client-side HTTP timeout
• operator-facing CLI and environment-variable interfaces stay unchanged
• project and crate contracts now describe the intended timeout behavior

Validation

• cargo fmt --all --check
• cargo test

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Restore bounded timeout for sparse-index HTTP requests

Building the reqwest client without .timeout(...) removes the only per-request deadline for sparse-index prefetch, and reqwest’s default is to wait indefinitely; in run_parallel_sparse_index_lookup, the scoped worker joins wait for every lookup to return, so a single stalled TCP/HTTP read can block cargo mono publish forever before publish retries ever run. This can deadlock CI release jobs on transient network hangs instead of failing fast and retrying.

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