The "Connecting to Telegram (attempt N/8)…" line logs at WARNING and
reaches the gateway's default stderr handler, but the matching
"Connected to Telegram (… mode)" line was INFO and went to the log file
only. A healthy startup therefore looked permanently hung at
"attempt 1/8" on the terminal — the logging-illusion half of #90835.
Promote the success line to WARNING so both sides of the connect
transition share the same console sink; a genuine hang is now the
absence of the success line. Adds an AST-level regression test pinning
the level pairing. Sibling adapters (homeassistant, wecom) log both
sides at INFO, so they don't have this asymmetry.
Fixes#90835
e2521fdef6