Follow-up on the salvaged fix, which bounded start_polling() only in
_handle_polling_network_error. The same wedge (#59614) exists at the two
sibling call sites:
1. _start_polling_resilient (bootstrap): an exhausted pool hangs connect()
forever. The TimeoutError from wait_for is a builtins TimeoutError
(OSError subclass), so the existing except classifies it via
_looks_like_network_error and schedules background recovery.
2. _handle_polling_conflict (conflict-retry ladder): identical hang wedges
conflict attempt N forever; timeout now converts to RuntimeError and the
existing except schedules the next attempt.
Tests replaced with a stronger suite: hung-network-ladder repro (RED without
the fix), bootstrap hang schedules recovery, success-path sanity, and a
bug-class contract test asserting EVERY updater.start_polling( call site is
wrapped in wait_for so a new unbounded site can't reintroduce the wedge.
Verified RED (3 failures) with the wrappers removed, GREEN with them.
When the connection pool is in a degraded state after
_drain_polling_connections(), start_polling() can hang indefinitely
when both primary and fallback Telegram endpoints are unreachable. The
httpx client may hold a stale socket that neither connects nor times out
within PTB's internal flow, causing the reconnect ladder to stall at
attempt 1/10 forever.
Wrap start_polling() in asyncio.wait_for() with a 30-second timeout so a
hung call raises asyncio.TimeoutError and feeds back into the existing
retry ladder. This unblocks:
- The 10-retry ladder advances to attempt 2, 3, ...
- The heartbeat loop sees _polling_error_task.done() and can trigger recovery
- The reconnect watcher gets the adapter in _failed_platforms
Fixes#59614
