Fix cargo clippy warnings across the workspace

- Derive Default for Config instead of manually mirroring each
  sub-config's Default impl
- Use std::io::Error::other instead of Error::new(ErrorKind::Other, ..)
- Drop the unused mut on the store lock in full_reindex
- Remove Store::dim, a field that was set once and never read
- Use char_indices().enumerate() instead of a hand-rolled loop counter
  in split_by_chars, and is_multiple_of() for the chunk boundary check
- Use strip_prefix instead of manual slicing in expand_home

(cherry picked from commit b740af38e17d04bd83db93bbb0585ed5744a436e)

breadmill/src/chunk.rs

@@ -81,10 +81,9 @@ fn split_by_chars(chunk: Chunk, max_chars: usize) -> Vec<Chunk> {
     let text = &chunk.text;
     let mut result = Vec::new();
     let mut seg_start = 0usize;
-    let mut count = 0usize;
 
-    for (byte_idx, _) in text.char_indices() {
-        if count > 0 && count % max_chars == 0 {
+    for (count, (byte_idx, _)) in text.char_indices().enumerate() {
+        if count > 0 && count.is_multiple_of(max_chars) {
             result.push(Chunk {
                 text: text[seg_start..byte_idx].to_string(),
                 start: chunk.start + seg_start,
@@ -92,7 +91,6 @@ fn split_by_chars(chunk: Chunk, max_chars: usize) -> Vec<Chunk> {
             });
             seg_start = byte_idx;
         }
-        count += 1;
     }
     if seg_start < text.len() {
         result.push(Chunk {

breadmill/src/indexer.rs

@@ -64,7 +64,7 @@ impl Indexer {
     pub fn full_reindex(&self) {
         eprintln!("breadmill: full reindex triggered");
         {
-            let mut store = self.state.store.lock_recover();
+            let store = self.state.store.lock_recover();
             // Clear all state
             let _ = store.conn.execute_batch("DELETE FROM chunks; DELETE FROM files;");
             let _ = store.index.reserve(4096);
@@ -416,9 +416,9 @@ fn sha256_str(bytes: &[u8]) -> String {
 }
 
 pub fn expand_home(path: &str) -> PathBuf {
-    if path.starts_with("~/") {
+    if let Some(rest) = path.strip_prefix("~/") {
         let home = std::env::var("HOME").unwrap_or_else(|_| "/tmp".into());
-        PathBuf::from(home).join(&path[2..])
+        PathBuf::from(home).join(rest)
     } else {
         PathBuf::from(path)
     }

breadmill/src/store.rs

@@ -6,7 +6,6 @@ use usearch::{Index, IndexOptions, MetricKind, ScalarKind, new_index};
 pub struct Store {
     pub conn: Connection,
     pub index: Index,
-    pub dim: usize,
 }
 
 // usearch::Index wraps a raw C++ pointer; access is serialized by the Mutex<Store>.
@@ -87,7 +86,7 @@ impl Store {
             index.reserve(4096).map_err(|e| e.to_string())?;
         }
 
-        Ok(Self { conn, index, dim })
+        Ok(Self { conn, index })
     }
 
     // ---- file state ---------------------------------------------------------