Resume spoken reading at sentence checkpoints

[hrhrng]

What changed

• persist read-aloud progress at fine sentence boundaries
• resume the first spoken passage from that durable checkpoint
• let a selected audio model replace the fictional readio-1 model slot
• keep voice and playback rate in the transport area without repeating the engine
• bump the TUI to 0.2.0-beta.10

Why

Quitting during a spoken passage restored only its paragraph window, which could replay from a chapter opening. The status row also reported the real TTS model and the fictional agent model at the same time.

Validation

• cargo fmt --check
• cargo clippy --all-targets -- -D warnings
• 410-test full suite
• targeted restart checkpoint, model-slot, and explicit-jump tests