Complete Epic 113 caller-owned vision

[rsasaki0109]

Summary

• expose explicit reusable GaussianBlurWorkspace ownership in Python while retaining the convenience pool
• report reserved Gaussian workspace bytes and verify warmed steady-state reuse
• close Epic 113 caller-owned output/workspace slices in the roadmap with a delivery receipt

Impact

Callers can now reuse both NumPy output storage and Gaussian scratch storage explicitly, matching the existing morphology, Canny, and exact EDT ownership contracts. SpatialRust remains at version 1.1.0.

Validation

• cargo test -p spatialrust-vision --no-default-features --features full
• cargo clippy --workspace --all-targets -- -D warnings (Rust 1.97.0)
• cargo clippy --workspace --all-features --lib -- -D warnings (Rust 1.97.0)
• RUSTFLAGS="-D warnings" cargo test --workspace --no-run
• cargo check --manifest-path crates/spatialrust-py/Cargo.toml
• python -m pytest crates/spatialrust-py/tests -q
• python -m mypy.stubtest spatialrust --ignore-missing-stub --allowlist crates/spatialrust-py/stubtest_allowlist.txt --ignore-unused-allowlist
• git diff --check