0.18.1 docs: refresh README, CHANGELOG, and docs/ for the trait split

The library's public-facing docs were sitting on the 0.17 trait
surface — Disc::copy, pes::Stream, SectorReader, etc. — even though
all in-tree callers migrated in 0.18 rounds 1-3. With 0.18.1 about
to ship, a user copy-pasting the README sample from crates.io would
have hit a compile error.

This commit is purely doc-side:

- README.md: Quick Start rewritten onto Disc::sweep + Disc::patch
  with caller-orchestrated multipass; Streams table footnote and
  Architecture row reference FrameSource / FrameSink.
- CHANGELOG.md: 0.18.1 entry describing the redesign — primitives,
  trait splits, deprecations (kept alive through 0.18.x, deletion
  target 0.18.2), throughput numbers.
- docs/{rip-recovery,api-design,architecture,disc-to-rip,
  drive-access,udf}.md: every Disc::copy / pes::Stream /
  SectorReader reference updated to the 0.18 trait surface.
- FEATURES.md: deleted (8+ versions stale; capabilities live in
  README.md and CHANGELOG.md now, matching the workspace-top
  FEATURES.md removal in 84acd65).
- examples/iso_dump.rs: verified compiles against 0.18.1.

No code changes.

See (internal)/memory/0_18_redesign.md.

Single contributor: MattJackson.

docs/drive-access.md

@@ -52,8 +52,8 @@ selects the per-CDB timeout:
 
 | `recovery` | Timeout  | Used by                                  |
 |------------|----------|------------------------------------------|
-| `false`    | 1.5 s    | `Disc::copy` fast skip-forward sweep, `DiscStream::fill_extents` |
-| `true`     | 30 s     | `Disc::patch` multi-pass over the mapfile |
+| `false`    | 1.5 s    | `Disc::sweep` fast skip-forward pass, `DiscStream::fill_extents` |
+| `true`     | 30 s     | `Disc::patch` retry pass over the mapfile |
 
 On any SCSI failure or timeout, `read` returns `Err(DiscRead)` immediately.
 There are no inline retries, no SCSI reset, no Phase 1/2/3 escalation.