v0.2.4 — Test Connection, close button, connection UI polish

What's new in v0.2.4

Connection dialog

• Test Connection button — verify your credentials before committing to a connection. Spawns a one-shot DB worker, reports success (green) or failure (red + error message) inline. The button disables itself during the test and resets cleanly on cancel.

Connection switcher (sidebar)

• Close button (×) — disconnect and remove any open connection with a single click. All tabs belonging to that connection are closed automatically; at least one tab is always preserved.
• Color-coded status dots — replaced broken emoji squares with rendered ● glyphs colored directly by egui: green = connected, yellow = connecting, red = error, gray = disconnected.
• + button — the new-connection button was using a fullwidth Unicode character that rendered as a blank square on some Windows systems; replaced with plain ASCII +.

Connection menu

• Group labels in the saved-profiles dropdown now use the same colored ● dots instead of emoji squares.

Internal

• DbCommand::TestConnection(ConnectionProfile) + DbEvent::TestResult { success, message } added to the channel protocol.
• TabManager::close_tabs_for_conn(conn_id) — new public method; always leaves ≥1 tab.
• ConnectionDialog gains test_clicked, testing, test_result fields; reset on reset().
• PgClientApp gains test_conn: Option<(Sender, Receiver)> for the one-shot test worker.

Full changelog

v0.2.3...v0.2.4