fix: use blocking sockets for daemon connections

[jlongster]

Summary

• Explicitly set accepted Unix sockets to blocking mode. On macOS they inherit the nonblocking listener mode, causing the subscription disconnect monitor to treat WouldBlock as a disconnected client.
• Extend the existing streaming test to verify delayed live output as well as initial replay.

Verification

• Reproduced streaming test failure on macOS before the fix; it passes after the fix.
• cargo test: all 13 tests pass.
• cargo fmt --check and cargo clippy --all-targets --all-features -- -D warnings pass.
• OpenCode server integration now exchanges input/output through both attachments, but still fails its separate foreground-process metadata assertion (both values remain null).

No OpenCode production build or protocol changes are required.