fix: contain panics across persisted loads - #49

Summary

• contain panics from lower-level persisted-page decoding and WorkTable reconstruction
• convert both dependency panics and ordinary decode errors into PersistenceLoadError
• cover the containment boundary with deterministic unit tests
• keep both crates at 1.0.0-beta.4

This addresses the all-features master failure in run 30957623797, where data_bucket panicked while parsing a torn unsized index page.

Validation

• cargo fmt --all
• cargo clippy --workspace --all-targets --all-features -- -D warnings
• exact regression: persistence::torn_shutdown::test_store_survives_torn_shutdowns
• cargo test --workspace --all-targets --all-features (all passed; 4 documented ignores)

Closes #41 once merged and green.