feat: first-draft preview-capable zosstorage

- CLI: add topology selection (-t/--topology), preview flags (--show/--report), and removable policy override (--allow-removable) (src/cli/args.rs)
- Config: built-in sensible defaults; deterministic overlays for logging, fstab, removable, topology (src/config/loader.rs)
- Device: discovery via /proc + /sys with include/exclude regex and removable policy (src/device/discovery.rs)
- Idempotency: detection via blkid; safe emptiness checks (src/idempotency/mod.rs)
- Partition: topology-driven planning (Single, DualIndependent, BtrfsRaid1, SsdHddBcachefs) (src/partition/plan.rs)
- FS: planning + creation (mkfs.vfat, mkfs.btrfs, bcachefs format) and UUID capture via blkid (src/fs/plan.rs)
- Orchestrator: pre-flight with preview JSON (disks, partition_plan, filesystems_planned, mount scheme). Skips emptiness in preview; supports stdout+file (src/orchestrator/run.rs)
- Util/Logging/Types/Errors: process execution, tracing, shared types (src/util/mod.rs, src/logging/mod.rs, src/types.rs, src/errors.rs)
- Docs: add README with exhaustive usage and preview JSON shape (README.md)

Builds and unit tests pass: discovery, util, idempotency helpers, and fs parser tests.

src/lib.rs

@@ -0,0 +1,20 @@
+//! Crate root for zosstorage: one-shot disk provisioning utility for initramfs.
+
+pub mod cli;
+pub mod logging;
+pub mod config;
+pub mod device;
+pub mod partition;
+pub mod fs;
+pub mod mount;
+pub mod report;
+pub mod orchestrator;
+pub mod idempotency;
+pub mod util;
+pub mod errors;
+pub mod types; // top-level types (moved from config/types.rs for visibility)
+
+pub use errors::{Error, Result};
+
+/// Crate version string from Cargo.
+pub const VERSION: &str = env!("CARGO_PKG_VERSION");