feat: complete relate and buffer strategy parity

[pentatonick]

Summary

• Complete relate and buffer strategy parity work

Test plan

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

[codecov-commenter]

⚠️ Please install the to ensure uploads and comments are reliably processed by Codecov.

Codecov Report

❌ Patch coverage is 93.46486% with 53 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
crates/geometry-overlay/src/relate.rs	92.76%	27 Missing ⚠️
crates/geometry-overlay/src/buffer.rs	94.60%	23 Missing ⚠️
crates/geometry-strategy/src/buffer.rs	75.00%	3 Missing ⚠️

📢 Thoughts on this report? Let us know!