v0.11.21: multi-pass rip — Disc::copy + Disc::patch + mapfile module

New primitives for two-stage rip workflows: fast forward pass with
zero-fill on failures, then targeted retries of bad ranges via a
ddrescue-compatible mapfile.

- Disc::copy now takes &CopyOptions (breaking change from positional
  args). Always writes a sidecar .mapfile. Opt-in skip_on_error +
  skip_forward give ddrescue-style fast sweep: 64 KB blocks,
  exponential skip-forward on failure, zero-fill bad blocks. Defaults
  preserve pre-0.11.21 behavior (recovery reads, abort on bad sector).

- Disc::patch is new and idempotent. Reads the mapfile, re-reads every
  non-finished range with full drive recovery, patches good bytes back
  into the ISO at exact offsets. Call N times for N retry attempts.

- disc::mapfile is a new module. ddrescue text format, crash-safe
  (flushed on every record()), greppable, human-editable, tool-compatible.
  Status chars match ddrescue: ? / * / / / - / +.

- Re-exports FileSectorReader from the crate root.

- freemkv CLI caller (pipe.rs) updated to the new Disc::copy signature
  in lockstep — shipped in the 0.11.21 freemkv CLI release.

Part of the 0.11.21 ecosystem sync (libfreemkv + freemkv + bdemu +
autorip all on 0.11.21).

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "libfreemkv"
-version = "0.11.18"
+version = "0.11.21"
 edition = "2021"
 rust-version = "1.86"
 license = "AGPL-3.0-only"