⬆️ 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/obikrope/src/cursor.rs

@@ -194,7 +194,10 @@ pub trait RopeCursor<'a> {
     /// Use the returned value with [`SeekMode::Rope`] to restore a position,
     /// or as a truncation point after a write pass.
     fn rope_tell(&self) -> usize {
-        self.state().current.get().unwrap_or(self.state().offset.get())
+        self.state()
+            .current
+            .get()
+            .unwrap_or(self.state().offset.get())
     }
 
     /// Number of bytes visible through this cursor (`rope.len() - offset`).
@@ -528,13 +531,13 @@ mod tests {
     use crate::Rope;
 
     fn rope(data: &[u8]) -> Rope {
-        let mut r = Rope::new();
+        let mut r = Rope::new(None);
         r.push(data.to_vec());
         r
     }
 
     fn rope2(a: &[u8], b: &[u8]) -> Rope {
-        let mut r = Rope::new();
+        let mut r = Rope::new(None);
         r.push(a.to_vec());
         r.push(b.to_vec());
         r
@@ -703,14 +706,14 @@ mod tests {
 
     #[test]
     fn backward_empty_rope_returns_error() {
-        let r = Rope::new();
+        let r = Rope::new(None);
         let c = r.bw_cursor();
         assert!(c.read_next().is_err());
     }
 
     #[test]
     fn forward_empty_rope_returns_error() {
-        let r = Rope::new();
+        let r = Rope::new(None);
         let c = r.fw_cursor();
         assert!(c.read_next().is_err());
     }

src/obikrope/src/rope.rs

@@ -28,6 +28,7 @@ use std::cell::Cell;
 ///
 /// See the [module-level documentation][crate::rope] for a full overview.
 pub struct Rope {
+    pub(crate) mime_type: Option<&'static str>,
     pub(crate) blocks: Vec<Vec<Cell<u8>>>,
     pub(crate) length: usize,
     pub(crate) start_block_idx: Vec<usize>,
@@ -35,8 +36,9 @@ pub struct Rope {
 
 impl Rope {
     /// Create an empty rope (no allocations).
-    pub fn new() -> Self {
+    pub fn new(mime_type: Option<&'static str>) -> Self {
         Self {
+            mime_type,
             blocks: Vec::new(),
             length: 0,
             start_block_idx: Vec::new(),
@@ -59,6 +61,11 @@ impl Rope {
         self.length += block_len;
     }
 
+    /// The MIME type of the rope, if known.
+    pub fn mime_type(&self) -> Option<&str> {
+        self.mime_type.as_deref()
+    }
+
     /// Total number of blocks.
     pub fn n_blocks(&self) -> usize {
         self.blocks.len()
@@ -115,7 +122,7 @@ impl Rope {
         }
 
         if pos == self.length {
-            return Ok(Rope::new());
+            return Ok(Rope::new(self.mime_type.clone()));
         }
 
         let (block_idx, from, _) = self.lookup(pos).ok_or_else(|| {
@@ -149,6 +156,7 @@ impl Rope {
         self.length = pos;
 
         Ok(Rope {
+            mime_type: self.mime_type.clone(),
             blocks: tail_blocks,
             length: tail_length,
             start_block_idx: tail_starts,
@@ -185,13 +193,13 @@ mod tests {
     }
 
     fn make(data: &[u8]) -> Rope {
-        let mut r = Rope::new();
+        let mut r = Rope::new(None);
         r.push(data.to_vec());
         r
     }
 
     fn make2(a: &[u8], b: &[u8]) -> Rope {
-        let mut r = Rope::new();
+        let mut r = Rope::new(None);
         r.push(a.to_vec());
         r.push(b.to_vec());
         r
@@ -201,7 +209,7 @@ mod tests {
 
     #[test]
     fn empty_rope_is_empty() {
-        let r = Rope::new();
+        let r = Rope::new(None);
         assert!(r.is_empty());
         assert_eq!(r.len(), 0);
         assert_eq!(r.n_blocks(), 0);
@@ -213,6 +221,7 @@ mod tests {
         assert!(!r.is_empty());
         assert_eq!(r.len(), 5);
         assert_eq!(r.n_blocks(), 1);
+        assert_eq!(r.mime_type(), None);
     }
 
     #[test]
@@ -220,6 +229,7 @@ mod tests {
         let r = make2(b"abc", b"de");
         assert_eq!(r.len(), 5);
         assert_eq!(r.n_blocks(), 2);
+        assert_eq!(r.mime_type(), None);
     }
 
     #[test]
@@ -261,7 +271,7 @@ mod tests {
 
     #[test]
     fn lookup_empty_rope_returns_none() {
-        assert!(Rope::new().lookup(0).is_none());
+        assert!(Rope::new(None).lookup(0).is_none());
     }
 
     #[test]