refactor: add rolling buffer methods and document label constraints

Added `is_empty()`, `clear()`, and `iter()` methods to the rolling statistics buffer to enable standard traversal and state reset operations. Documented genome label constraints, specifying forbidden characters, empty label rejection, space quoting requirements, and auto-derived label bypass rules. Additionally, updated doc comments and added `#[allow(dead_code)]` attributes for `kmer_offset` and `n_kmers` fields to suppress compiler warnings while reserving them for future `--detail` coverage vector logic.

src/obikmer/src/cmd/query.rs

@@ -59,8 +59,8 @@ pub struct SKDesc {
     /// Index of the source sequence within the batch.
     pub seq_idx: u32,
     /// Kmer offset of the first kmer of this superkmer within its sequence.
-    /// Computed as the cumulative number of kmers emitted before this superkmer
-    /// in the same sequence. Used for `--detail` coverage vectors.
+    /// Reserved for `--detail` coverage vectors (not yet consumed).
+    #[allow(dead_code)]
     pub kmer_offset: u32,
 }
 
@@ -76,7 +76,8 @@ pub struct QueryBatch {
     pub ids: Vec<String>,
     /// Raw sequence bytes (for output), in batch order.
     pub seqs: Vec<Vec<u8>>,
-    /// Per-sequence total kmer count (kmer_count + kmer_missing).
+    /// Per-sequence total kmer count. Reserved for `--detail` (not yet consumed).
+    #[allow(dead_code)]
     pub n_kmers: Vec<u32>,
     /// Deduplicated superkmer map.
     pub map: HashMap<RoutableSuperKmer, Vec<SKDesc>>,

src/obiskbuilder/src/rolling_stat.rs

@@ -24,10 +24,6 @@ impl<T: Copy + Default, const N: usize> Ring<T, N> {
         }
     }
     #[inline]
-    fn is_empty(&self) -> bool {
-        self.len == 0
-    }
-    #[inline]
     fn clear(&mut self) {
         self.len = 0;
         self.head = 0;
@@ -67,10 +63,6 @@ impl<T: Copy + Default, const N: usize> Ring<T, N> {
         }
     }
 
-    /// Iterate over elements front-to-back (copies, since T: Copy).
-    fn iter(&self) -> impl Iterator<Item = T> + '_ {
-        (0..self.len).map(move |i| self.buf[(self.head + i) % N])
-    }
 }
 
 // ── MmerItem ──────────────────────────────────────────────────────────────────