disc/patch: fast_capture mode — breadth-first recovery (#50)

A PatchOptions.fast_capture pass reads each bad range ONCE at the full batch and
leaves every FAILED block NonTrimmed for a later pass — no bisect, no per-sector
grind, no retry. This lets a first retry pass grab the readable blocks (the
sweep's good skip-ahead overshoot) of EVERY section quickly, before any single
section's slow per-sector recovery — instead of grinding section 1 to exhaustion
before even touching section 2. A later pass (fast_capture = false) does the
granular bisect/retry on what's left.

Load-bearing invariant (fixture test): NO data is dropped. A failed block becomes
NonTrimmed (pending, retried by a granular pass), NEVER Unreadable. The test pins
that the readable half of a range recovers, the bad half stays NonTrimmed (not
Unreadable), and the bad block is marked in ONE batch read with zero bisection.
Disc::copy's internal patch keeps fast_capture=false (single-call full recovery).

tests/pass_n_size_aware_skip.rs

@@ -275,6 +275,7 @@ fn patch_block_sectors_zero_does_not_busy_spin() {
         progress: None,
         halt: Some(halt.clone()),
         key_fetch: None,
+        fast_capture: false,
     };
 
     let outcome = disc.patch(&mut reader, &iso_path, &opts);