Reflect improvise-8zh: `persistence/` and `import/` now live in the
`improvise-io` sub-crate under `crates/`.
- Sub-crate list expanded to describe improvise-io's scope, its
dependencies (improvise-core, improvise-formula), and the
standalone-build guarantee.
- File Inventory reorganized: "Import layer" + persistence entries
collapsed into a single "I/O crate layers" block with paths rooted at
`crates/improvise-io/src/`.
- Updated line/test counts to current contents.
- Top-level block trimmed (persistence/format no longer live there) and
lib.rs annotated as a re-export facade.
No consumer-facing path changes; `crate::persistence::*` and
`crate::import::*` still resolve via the main crate's re-exports.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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