perf(filter): drop per-call `format!("{:?}", state).to_lowercase()` on SSH connection-state filter

[obchain]

Where

src/filter.rs:388

// Check connection state
let state_str = format!("{:?}", info.connection_state).to_lowercase();
if match_text(&state_str, fv) {
    return true;
}

What

The SSH branch of matches_application_filter derives the matchable connection-state string by Debug-formatting SshConnectionState and lowercasing the result. Two heap allocations per SSH connection per filter criterion per render frame:

1. format!("{:?}", …) builds a new String via the Debug impl.
2. .to_lowercase() walks that string and builds another String.

Both allocations are pure waste — SshConnectionState is a fieldless 4-variant enum (Banner, KeyExchange, Authentication, Established) whose lower-case canonical form is known at compile time and can be a &'static str.

Why it matters

Filter evaluation runs over every visible SSH connection on every render tick whenever a non-empty filter query is active. The cost is small per call but cumulative — and conceptually wrong: Debug output is not a stable user-facing string and shouldn't be repurposed as a filter token.

Suggested fix

Replace the format! + to_lowercase with an exhaustive match returning &'static str. The compiler enforces sync with the enum at compile time, so future variants can't silently drift out of filter coverage.