test(remote): qualify daemon async reuse

[jleni]

Summary

• replace the explicit sync --push shortcut with a process-level daemon upload → independent client remote HIT test
• use separate source trees, caches, configs, runtimes, and outputs; require matching keys, zero consumer compiler runs, and byte-identical artifacts
• pin the fixture config against inherited KACHE_* overrides and make daemon cleanup wait on the portable lifetime lock
• update the E2E coverage inventory now that the async production path is qualified

Falsification

I temporarily replaced the daemon worker's do_upload call with an injected error. The revised test failed at the remote publication boundary with no manifest or pack present; restoring the worker made it green. The fault was fully reverted before commit.

Validation

• cargo fmt --all -- --check
• git diff --check
• cargo clippy --workspace --all-targets --all-features -- -D warnings
• ./scripts/with-test-resources.sh cargo test --workspace --all-features
• cargo test --test filesystem_remote_test -- --nocapture (7/7)
• poisoned-env run with KACHE_REMOTE_READONLY=1 KACHE_LOCAL_ONLY=1 KACHE_DISABLED=1
• independent static review; all findings resolved

Closes #696