Release v0.6.0

[roelvangils]

Summary

Workspace version bumped from `0.5.0` to `0.6.0`. All internal path-deps updated. CHANGELOG `[Unreleased]` renamed to `[0.6.0] - 2026-05-07`; fresh empty `[Unreleased]` block stays on top.

After this PR merges, push the `v0.6.0` tag (`git tag v0.6.0 && git push origin v0.6.0`) and the release workflow builds unsigned binaries for Linux x86_64, macOS arm64 (with Metal Whisper acceleration), and Windows x86_64.

What ships in 0.6.0

Two big additions on top of v0.5.0's feature-complete v1 candidate:

Word-level Media Overlay sync (M6.5)

whisper.cpp's per-token timestamps now drive karaoke-style highlight-along-with-audio in compatible reading systems (Thorium, Readium, Colibrio). BPE tokens are coalesced back into whole words via a leading-space rule with punctuation attachment; each word becomes one SMIL `` wrapped in a per-paragraph ``. Default-on; `--no-word-sync` opts out.

Materially valuable for dyslexic readers, language learners, and low-vision users tracking with magnifiers — a class of accessibility experience no other open-source DAISY → EPUB toolchain ships.

First-run UX overhaul

Five-command path from fresh clone to working binary:

```sh
brew install cmake epubcheck ffmpeg
git clone https://github.com/11ways/dpub && cd dpub
./scripts/build.sh # auto-picks Metal on Apple Silicon
./target/release/dpub setup --whisper-model medium # SHA-verified download
./target/release/dpub doctor # confirms everything green
```

• `dpub doctor` — diagnostic for build state (version + GPU acceleration), runtime tools (`epubcheck`, `ace`, `ffmpeg`), and Whisper model cache. `--json` for CI.
• `dpub setup --whisper-model ` — downloads `tiny` / `base` / `small` / `medium` / `large-v3` with SHA256 verification.
• `scripts/build.sh` — host-aware release build (Metal on Apple Silicon, CUDA on Linux+nvcc, CPU otherwise).
• `--transcribe` auto-discovers cached models; interactive TTY prompt offers to download `ggml-medium.bin` when none is cached.
• `dpub doctor --install` — opt-in installer for missing tools via `brew` / `apt-get` / `dnf` with per-tool consent.

Test plan

• `cargo build --workspace` clean at v0.6.0.
• `cargo test --workspace` — all 25 suites green.
• `cargo clippy --all-targets -- -D warnings` — clean.
• After merge: tag push fires the release workflow; verify each platform's artefact runs (`dpub --version` prints `dpub 0.6.0`, `dpub doctor` works).