fix: preserve ECH discovery timeout errors

[ryanfowler]

Summary

• propagate exhausted connect timeout budgets before ECH discovery
• share HTTP ECH lookup and error policy with WebSocket discovery
• preserve required-mode DNS errors and automatic GREASE warnings
• add HTTP/WebSocket exhausted-budget and WebSocket error-policy tests

Validation

• cargo fmt --check
• cargo clippy --locked --all-targets --all-features -- -D warnings
• cargo test --locked --all-features --lib --bins
• cargo test --locked --all-features --test cli --test formatting --test grpc --test har --test http --test install --test network --test terminal --test update --test websocket -- --test-threads=2