feat(ai-formatting): collapse adjacent repetitions in Clean/Smart modes + chore(audio): swap deprecated cpal .name() for description-based helper

ai-formatting:
  - rule_based.rs: collapse_repetitions() merges adjacent duplicate
    tokens like 'I I can' -> 'I can' and 'think think that' -> 'think
    that'. Normalises case and punctuation before comparison.
  - pipeline.rs: post_process now calls collapse_repetitions when
    format_mode is Clean or Smart. Added unit coverage.

audio:
  - capture.rs: replace the seven deprecated cpal DeviceTrait::name()
    call sites with a device_display_name() helper that uses the
    non-deprecated description() path. Keeps identical behaviour,
    silences compile warnings, ready for cpal upgrade.

Addresses the 'Christ. Christ.' live-transcription boundary duplicate
Jake saw during Group 1 dogfooding. Does not fix all cross-chunk
overlap cases (see live.rs OVERLAP_SAMPLES for the root cause) but
catches the common stutter pattern at post-processing.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

crates/ai-formatting/src/pipeline.rs

@@ -47,6 +47,7 @@ pub fn post_process_segments(segments: &mut Vec<Segment>, options: &PostProcessO
             seg.text = rule_based::to_british_english(&seg.text);
         }
         if options.format_mode != FormatMode::Raw {
+            seg.text = rule_based::collapse_repetitions(&seg.text);
             seg.text = rule_based::format_text(&seg.text);
         }
     }
@@ -134,4 +135,24 @@ mod tests {
 
         assert!(segments[2].text.starts_with("\n\n"));
     }
+
+    #[test]
+    fn post_process_collapses_repeated_phrases_in_clean_modes() {
+        let mut segments = vec![Segment {
+            start: 0.0,
+            end: 1.0,
+            text: "I need I need to go to the shops".into(),
+        }];
+        let options = PostProcessOptions {
+            remove_fillers: false,
+            british_english: false,
+            anti_hallucination: false,
+            format_mode: FormatMode::Clean,
+            dictionary_terms: vec![],
+        };
+
+        post_process_segments(&mut segments, &options);
+
+        assert_eq!(segments[0].text, "I need to go to the shops");
+    }
 }

crates/ai-formatting/src/rule_based.rs

@@ -28,6 +28,12 @@ static FILLER_REGEXES: LazyLock<Vec<regex_lite::Regex>> = LazyLock::new(|| {
         .collect()
 });
 
+fn normalise_repetition_token(token: &str) -> String {
+    token
+        .trim_matches(|ch: char| !(ch.is_alphanumeric() || ch == '\'' || ch == '-'))
+        .to_lowercase()
+}
+
 /// Remove common filler words from transcription text (case-insensitive).
 pub fn remove_fillers(text: &str) -> String {
     let mut result = text.to_string();
@@ -54,6 +60,77 @@ pub fn remove_fillers(text: &str) -> String {
     collapsed.trim().to_string()
 }
 
+/// Collapse obvious stutters and immediate repeated short phrases.
+///
+/// Examples:
+/// - `I I can` -> `I can`
+/// - `I need I need to go` -> `I need to go`
+/// - `Think think that's that` -> `Think that's that`
+pub fn collapse_repetitions(text: &str) -> String {
+    if text.trim().is_empty() {
+        return String::new();
+    }
+
+    let tokens: Vec<&str> = text.split_whitespace().collect();
+    if tokens.len() < 2 {
+        return text.trim().to_string();
+    }
+
+    let normalised: Vec<String> = tokens
+        .iter()
+        .map(|token| normalise_repetition_token(token))
+        .collect();
+    let mut kept_indices: Vec<usize> = Vec::with_capacity(tokens.len());
+    let mut i = 0;
+
+    while i < tokens.len() {
+        let mut skipped_phrase = false;
+
+        for phrase_len in (1..=3).rev() {
+            if kept_indices.len() < phrase_len || i + phrase_len > tokens.len() {
+                continue;
+            }
+
+            let repeated = (0..phrase_len).all(|offset| {
+                let prev_index = kept_indices[kept_indices.len() - phrase_len + offset];
+                let prev = &normalised[prev_index];
+                let upcoming = &normalised[i + offset];
+                !prev.is_empty() && prev == upcoming
+            });
+
+            if repeated {
+                i += phrase_len;
+                skipped_phrase = true;
+                break;
+            }
+        }
+
+        if skipped_phrase {
+            continue;
+        }
+
+        if let Some(&last_index) = kept_indices.last() {
+            let current = &normalised[i];
+            let previous = &normalised[last_index];
+            if !current.is_empty() && current == previous {
+                i += 1;
+                continue;
+            }
+        }
+
+        kept_indices.push(i);
+        i += 1;
+    }
+
+    kept_indices
+        .into_iter()
+        .map(|index| tokens[index])
+        .collect::<Vec<_>>()
+        .join(" ")
+        .trim()
+        .to_string()
+}
+
 /// Replacement pairs for American to British English conversion.
 ///
 /// All entries are plain base words (no regex metacharacters). The
@@ -260,6 +337,27 @@ mod tests {
         assert!(to_british_english("the color is red").contains("colour"));
     }
 
+    #[test]
+    fn collapse_repetitions_removes_consecutive_duplicate_words() {
+        assert_eq!(collapse_repetitions("I I can do that"), "I can do that");
+        assert_eq!(
+            collapse_repetitions("Think think that's that"),
+            "Think that's that"
+        );
+    }
+
+    #[test]
+    fn collapse_repetitions_removes_repeated_short_phrases() {
+        assert_eq!(
+            collapse_repetitions("I need I need to go to the shops"),
+            "I need to go to the shops"
+        );
+        assert_eq!(
+            collapse_repetitions("We should review we should review the draft"),
+            "We should review the draft"
+        );
+    }
+
     #[test]
     fn format_text_capitalises_after_full_stops() {
         let result = format_text("hello world. this is a test");