Pass-N recovery is now a chain of time-bounded recovery handlers instead
of one monolithic per-range loop that could grind the front of a bad
range for up to 30 min, wedge the drive, and abort the whole pass.
A bad range is a SubRanges set; recovery is an ordered list of
SectionHandlers (Linear{reverse,fast} covering back/forward x fast/slow,
and Bisect). A coordinator runs each handler with a hard per-handler
deadline: a handler recovers what it can (removing it from the still-bad
set) and hands the rest to the next handler; whatever is still bad after
the chain becomes NonTrimmed residue and we move on to the next range.
Guarantees, now structural rather than bolted-on:
- never hangs: every handler is deadline-bounded; the loop always drains
to recovered-or-residue.
- always moves on: a range that cannot be finished leaves residue and
advances; only a genuine transport fault or user halt ends the pass.
- extensible: a new recovery idea is one SectionHandler impl added to the
chain; a proven-ineffective one is removed. The engine never changes.
Removes ~1.9k lines of the old inner loop (watchdogs, skip escalation,
NOT_READY grind, wedge counters) and their tests. fast_capture is now
inert (the chain supersedes it); breadth-first ordering becomes a future
scheduler concern. New module: disc/section_recover.rs (8 fixture tests,
injectable clock — bounded/never-hang proven without touching a drive).
Two A/B tests updated to the chain's strictly-better recovery counts.
Matthew Jackson
d65b776a8e