v0.13.21 — bisect-on-fail in Disc::copy + 10s caller READ timeout

Fixes the BU40N wedge cycle that has been chasing us through
v0.13.18-20. Two changes, both backed by empirical live-hardware
probes recorded in freemkv-private/docs/TEST_PLAN.md:

1. scsi/mod.rs: READ_TIMEOUT_MS 1500 → 10000 ms.
   Cold-start seek on the BU40N takes ~1.5 s. The old timeout
   cancelled normal reads at the boundary, triggering the kernel's
   ABORT/RESET escalation, which the Initio bridge couldn't drain —
   firmware-level wedge. 10 s catches every legitimate slow read
   (max successful ECC recovery: 2.6 s; cold-start: 1.5 s) with
   margin and short-circuits truly bad sectors at ~10 s.

2. disc/mod.rs: Disc::copy bisect-on-fail (replaces skip-forward).
   Live data showed the drive fails multi-sector READs in the bad
   zone but reads each sector cleanly when asked at bpt=1. Old
   skip-forward jumped 845 MB on the first multi-sector failure,
   marking everything in between as bad — losing clean territory
   sandwiched between bad sectors. New algorithm bisects: split the
   failed block in half, retry each half, recurse to single-sector
   reads. Sectors recoverable individually are picked up in Pass 1;
   only sectors that fail at bpt=1 are marked NonTrimmed for the
   patch passes. Stack-based DFS, log2(batch) = 6 levels for the
   default 60-sector batch.

Multi-pass machinery is untouched. Pass 2..N walk the mapfile and
become fast no-ops when bisect already recovered everything.
Wedged-drive early-exit, 30 s settle, batch taper, F-R-F-R direction
alternation — all preserved.

New test: integration_progress_and_halt::
test_disc_copy_bisect_recovers_via_single_sector_reads — synthetic
BU40N-pattern reader (multi-sector reads fail, single-sector
succeed). Pre-patch: lost everything to skip-forward. Post-patch:
100 % bytes_good. Plus the 10 sense-key parser tests from the
0.13.20 test-coverage pass.

Empirical recovery on Dune 2 UHD on the BU40N (per TEST_PLAN.md run
log): old algorithm ~25 GB recovered + 6 GB skipped-forward and
mostly lost; new algorithm projects ~99 % recovery in Pass 1.

Audits + raw probe data:
- freemkv-private/docs/TEST_PLAN.md (run log)
- freemkv-private/docs/audits/2026-04-26-scsi-architecture-research.md

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "libfreemkv"
-version = "0.13.20"
+version = "0.13.21"
 edition = "2024"
 rust-version = "1.86"
 license = "AGPL-3.0-only"