Follow-ups on the #101406 salvage (#101391):
- The issue's measured incident was a healthy connect followed by silent
polling loss; nothing republished for 11 h. `_schedule_polling_recovery`
(the single entry to the recovery ladder) now publishes "retrying" while
the adapter is running; `_record_polling_progress` already flips it back.
- `BasePlatformAdapter.send_path_degraded` property (default False) replaces
the runner's `getattr(adapter, "_send_path_degraded")` reach into a
plugin-private attribute; Telegram overrides it. `_mark_connected()` reads
the property instead of taking a `degraded=` kwarg, and `_mark_degraded()`
+ `DEGRADED_STATUS_MESSAGE` replace three copies of the same write/string.
- The startup connect stamp (sibling of the reconnect stamp) honours the
same flag.
- Tests: mid-session death publishes retrying; pre-connect death does not;
progress never flips while not running / fatal; runner reconnect stamp
honours the adapter flag.
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