The adapter's private thread-deadline helper was the ancestor of the
unified deadline layer's run_bounded_async (#85147 was extracted from
it, plus the caller-cancellation leak fix the original still lacked).
Consolidate: the helper body becomes a thin wrapper mapping
BoundedResult.timed_out back to the asyncio.TimeoutError its 9 call
sites (the PTB retry ladder) expect. ~90 duplicated lines die, along
with the adapter-local copies of the abandon-cleanup runner and the
blocked-loop faulthandler diagnostics (both live in agent/deadline.py).
Everything the call sites rely on is preserved by the unified layer:
- thread-timer deadline that survives a blocked event loop (#63309)
- abandonment of cancellation-shielded tasks (PTB/httpcore anyio init)
- detached best-effort on_abandon cleanup (no httpx pool leak per retry)
- off-loop stack dump when the loop never processes the expiry
Plus one behavior IMPROVEMENT inherited from the shared copy: a caller
cancelling the wrapper no longer leaks the inner task unobserved (the
telegram original had that leak; the extraction fixed it).
test_telegram_init_deadline.py: the #63309 diagnostics probe now pins
the shared layer's dump hook (label "telegram-init") — same contract,
new seam. Wedge + cleanup-crash tests pass unchanged.
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