Add unified backend trait and polymorphic command dispatch #15

	name: CI

	# 1. When the workflow runs
	on:
	push: # any git push
	branches: ["**"] # all branches
	pull_request: # and every PR

	# 2. Single job called "build"
	jobs:
	build:
	runs-on: ubuntu-latest # GitHub-hosted Ubuntu runner
	timeout-minutes: 20 # hard stop to avoid hanging

	steps:
	# -- Step 1: Check out code
	- name: Checkout repository
	uses: actions/checkout@v4

	# -- Step 2: Cache Cargo downloads + build artefacts
	# Speeds up repeated runs dramatically
	- name: Cache cargo registry + target/
	uses: actions/cache@v4
	with:
	path: \|
	~/.cargo/registry
	~/.cargo/git
	target
	key: ${{ runner.os }}-cargo-${{ hashFiles('**/Cargo.lock') }}
	restore-keys: ${{ runner.os }}-cargo-

	# -- Step 3: Install Rust (stable channel, 2024 edition ready)
	- name: Install Rust toolchain
	uses: actions-rs/toolchain@v1
	with:
	toolchain: stable
	override: true
	components: clippy # we need clippy for linting

	# -- Step 4: Build & type-check the whole workspace
	- name: cargo check
	run: cargo check --workspace --all-features --locked

	# -- Step 5: Run clippy linter and fail on warnings
	- name: cargo clippy (deny warnings)
	run: cargo clippy --workspace --all-features --locked -- -D warnings

	# -- Step 6: Run the test suite
	- name: cargo test
	run: cargo test --workspace --all-features --locked

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