⬆️ refactor superkmer to use obipipeline

- Replace manual threading with Pipeline abstraction from `obipipline`
- Remove crossbeam-channel dependency and format detection logic
- Introduce typed `PipelineData` enum for pipeline stages (RawChunk, Norm Chunk, Batch)
- Implement shared normalization and extraction steps as `SharedFn`ƒ
  - Add unsafe Send/Sync impls for PipelineData (Rope ownership is moved, not shared)
- Replace manual reader/worker/output threads with a single Pipeline execution
  - Uses `make_source_fallible!`, shared transform functions, and a sink for output
- Simplify argument handling (remove `--format` flag)
  - Update Cargo.toml: remove crossbeam-channel, add obipipeline

src/obiskbuilder/src/iter.rs

@@ -156,7 +156,7 @@ mod tests {
     use obikrope::Rope;
 
     fn make_rope(data: &[u8]) -> Rope {
-        let mut r = Rope::new();
+        let mut r = Rope::new(None);
         r.push(data.to_vec());
         r
     }
@@ -210,7 +210,7 @@ mod tests {
     fn multi_slice_rope() {
         let data = b"ACGTACGTACGT\x00";
         let mid = data.len() / 2;
-        let mut rope = Rope::new();
+        let mut rope = Rope::new(None);
         rope.push(data[..mid].to_vec());
         rope.push(data[mid..].to_vec());
         let out: Vec<Vec<u8>> = SuperKmerIter::new(&rope, 4, 2, 1, 0.0)