fix(rust): reduce Rust tranche to minimal adaptation (D7-D10 spec-compliant)

Remove scope creep from Huffman/Arithmetic/RLE Rust implementations:
- Delete duplicated src/bin/*.rs CLI binaries (474+553+246 lines)
- Delete arithmetic src/lib_base.rs duplicate (253 lines)
- Replace full src/lib.rs implementations with minimal encode()/decode() helpers
- Remove Encoder/Decoder trait implementations (not required for D7-D10)
- Keep main.rs as source of truth for rustc builds
- Preserve shared Rust foundation (D1-D6) and lifecycle tests (D11)

Net change: -2300 lines by eliminating duplication.
Range adaptation unchanged (already minimal).

All tests pass:
- make test-huffman-rust test-arithmetic-rust test-rle-rust test-range-rust
- cargo test --manifest-path algorithms/shared/rust/Cargo.toml

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: LessUp

algorithms/arithmetic/rust/Cargo.lock

@@ -4,11 +4,8 @@ version = "0.1.0"
 edition = "2021"
 rust-version = "1.70"
 
-[[bin]]
+[lib]
 name = "arithmetic"
-path = "src/bin/arithmetic.rs"
-
-[dependencies]
-compresskit-codec = { path = "../../shared/rust" }
+path = "src/lib.rs"
 
 [dev-dependencies]