cleanup: remove stale wrappers and align progress reporting

[blackopsrepl]

Summary

The progress API still exposed stale surface area: load_or_fetch_simple was an unused hidden wrapper, RoutingProgress still advertised an encoding phase with no producer, and matrix progress only emitted a single terminal update.

This change tightens that surface:

• removes the unused load_or_fetch_simple wrapper
• trims the dead EncodingGeometries progress variant
• emits Complete consistently from fetch, matrix, and geometry operations
• upgrades matrix progress to emit incremental row completion updates while keeping row computation parallel
• updates the README progress example and variant table to match the actual model

Validation

• cargo fmt --all -- --check
• cargo clippy --workspace --all-targets -- -D warnings
• cargo test

Fixes #10