Add a local CI script, an installable pre-push hook, and contributor docs so contributors can run the same high-signal format, lint, test, feature-matrix, packaging, and release-bundle checks locally before opening or pushing a PR.

Constraint: Local workflow should stay as close to GitHub CI as practical without requiring a perfectly clean working tree
Constraint: README-linked contributor docs should also ship in local package and release artifact docs
Rejected: Keep pre-push guidance ad hoc in docs only | too easy to skip and drift from CI
Confidence: high
Scope-risk: narrow
Reversibility: clean
Directive: When CI steps change, update scripts/local-ci.sh, the hook installer, and contributor docs in the same change
Tested: scripts/install-git-hooks.sh; scripts/local-ci.sh; cargo fmt --all -- --check; cargo clippy --all-targets -- -D warnings; cargo test; cargo check --no-default-features; cargo check --no-default-features --features osd; cargo check --no-default-features --features local-rewrite; cargo package --locked --allow-dirty; cargo check --no-default-features --features cuda; cargo check --no-default-features --features cuda,local-rewrite; scripts/build-release-bundle.sh
Not-tested: Hook execution from a separate fresh clone