style: apply cargo fmt across the crate (A20)

The repo never enforced rustfmt, so formatting had drifted broadly. This is a
single mechanical `cargo fmt` pass over the whole crate (no behavioral change;
lib suite green, 493 passed). Going forward fmt should be enforced (planned CI
fmt --check step). Part of the 0.6.1 hygiene pass.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/dsp/aec.rs

@@ -283,8 +283,14 @@ mod tests {
         let q = echo.len() / 4;
         let early = erle(&echo[..q], &cleaned[..q]);
         let late = erle(&echo[3 * q..], &cleaned[3 * q..]);
-        assert!(late > early + 10.0, "should improve markedly: early {early:.1} late {late:.1}");
-        assert!(late > 20.0, "converged ERLE should exceed 20 dB, got {late:.1}");
+        assert!(
+            late > early + 10.0,
+            "should improve markedly: early {early:.1} late {late:.1}"
+        );
+        assert!(
+            late > 20.0,
+            "converged ERLE should exceed 20 dB, got {late:.1}"
+        );
     }
 
     #[test]
@@ -307,7 +313,10 @@ mod tests {
         let mut aec = Nlms::new(128, 0.5, 1e-6);
         let out = aec.process(&silent_ref, &near);
         for (a, b) in near.iter().zip(&out) {
-            assert!((a - b).abs() < 1e-6, "near-end should pass through: {a} vs {b}");
+            assert!(
+                (a - b).abs() < 1e-6,
+                "near-end should pass through: {a} vs {b}"
+            );
         }
     }
 
@@ -341,14 +350,24 @@ mod tests {
         let mut late_hits = 0;
         for i in 0..far.len() {
             if dtd.update(far[i], mic[i]) {
-                if i < onset { early_hits += 1 } else { late_hits += 1 }
+                if i < onset {
+                    early_hits += 1
+                } else {
+                    late_hits += 1
+                }
             }
         }
         // Echo-only stretch should rarely trip; near-end stretch should trip a lot.
         let early_rate = early_hits as f32 / onset as f32;
         let late_rate = late_hits as f32 / (far.len() - onset) as f32;
-        assert!(early_rate < 0.10, "false-positive rate {early_rate:.2} too high");
-        assert!(late_rate > 0.50, "missed double-talk, rate only {late_rate:.2}");
+        assert!(
+            early_rate < 0.10,
+            "false-positive rate {early_rate:.2} too high"
+        );
+        assert!(
+            late_rate > 0.50,
+            "missed double-talk, rate only {late_rate:.2}"
+        );
     }
 
     #[test]
@@ -380,6 +399,9 @@ mod tests {
             erle_dtd > erle_no + 15.0,
             "DTD should hold the echo path: with {erle_dtd:.1} dB vs without {erle_no:.1} dB"
         );
-        assert!(erle_dtd > 15.0, "held filter should still cancel echo: {erle_dtd:.1} dB");
+        assert!(
+            erle_dtd > 15.0,
+            "held filter should still cancel echo: {erle_dtd:.1} dB"
+        );
     }
 }

src/dsp/echo_path.rs

@@ -115,7 +115,10 @@ mod tests {
         let path = EchoPath::synthetic(480, 480, 0.5, 99);
         let echo = path.apply(&far);
         let ratio = rms(&echo) / rms(&far);
-        assert!((0.3..0.7).contains(&ratio), "echo/far rms ratio {ratio} off target");
+        assert!(
+            (0.3..0.7).contains(&ratio),
+            "echo/far rms ratio {ratio} off target"
+        );
     }
 
     #[test]

src/dsp/fft.rs

@@ -141,7 +141,10 @@ mod tests {
         buf[0] = Complex::new(1.0, 0.0);
         fft(&mut buf);
         for c in &buf {
-            assert!(approx(c.magnitude(), 1.0, 1e-9), "expected flat 1.0, got {c:?}");
+            assert!(
+                approx(c.magnitude(), 1.0, 1e-9),
+                "expected flat 1.0, got {c:?}"
+            );
         }
     }
 

src/dsp/metrics.rs

@@ -62,11 +62,31 @@ pub struct Band {
 
 /// Voice-relevant bands for spotting *where* residual echo or noise lives.
 pub const VOICE_BANDS: &[Band] = &[
-    Band { label: "low (80-300)", low_hz: 80.0, high_hz: 300.0 },
-    Band { label: "low-mid (300-1k)", low_hz: 300.0, high_hz: 1000.0 },
-    Band { label: "mid (1k-3k)", low_hz: 1000.0, high_hz: 3000.0 },
-    Band { label: "high-mid (3k-6k)", low_hz: 3000.0, high_hz: 6000.0 },
-    Band { label: "high (6k-12k)", low_hz: 6000.0, high_hz: 12000.0 },
+    Band {
+        label: "low (80-300)",
+        low_hz: 80.0,
+        high_hz: 300.0,
+    },
+    Band {
+        label: "low-mid (300-1k)",
+        low_hz: 300.0,
+        high_hz: 1000.0,
+    },
+    Band {
+        label: "mid (1k-3k)",
+        low_hz: 1000.0,
+        high_hz: 3000.0,
+    },
+    Band {
+        label: "high-mid (3k-6k)",
+        low_hz: 3000.0,
+        high_hz: 6000.0,
+    },
+    Band {
+        label: "high (6k-12k)",
+        low_hz: 6000.0,
+        high_hz: 12000.0,
+    },
 ];
 
 /// Sums the linear magnitude energy within `[low_hz, high_hz)` across a single

src/dsp/render.rs

@@ -202,7 +202,8 @@ fn legend(opts: &RenderOpts) -> String {
     if opts.ascii {
         for i in 0..steps {
             let v = i as f32 / (steps - 1) as f32;
-            let idx = ((v * (ASCII_RAMP.len() - 1) as f32).round() as usize).min(ASCII_RAMP.len() - 1);
+            let idx =
+                ((v * (ASCII_RAMP.len() - 1) as f32).round() as usize).min(ASCII_RAMP.len() - 1);
             s.push(ASCII_RAMP[idx] as char);
         }
     } else {
@@ -243,7 +244,11 @@ mod tests {
     fn render_produces_grid_of_expected_height() {
         let sig = generators::sine(2000.0, 0.8, 48_000, 48_000);
         let spec = stft::analyze(&sig, 48_000, 1024, 512);
-        let opts = RenderOpts { width: 40, height: 10, ..Default::default() };
+        let opts = RenderOpts {
+            width: 40,
+            height: 10,
+            ..Default::default()
+        };
         let out = render(&spec, &opts);
         // Header + 10 body rows + time axis (2) + legend = non-trivial.
         let lines = out.lines().count();

src/dsp/stft.rs

@@ -94,7 +94,10 @@ mod tests {
             .unwrap()
             .0;
         let peak_hz = s.bin_hz(peak_bin);
-        assert!((peak_hz - freq as f32).abs() < 100.0, "peak at {peak_hz} Hz, want {freq}");
+        assert!(
+            (peak_hz - freq as f32).abs() < 100.0,
+            "peak at {peak_hz} Hz, want {freq}"
+        );
     }
 
     #[test]

src/dsp/wav.rs

@@ -34,7 +34,12 @@ pub fn read(path: &Path) -> Result<WavData, String> {
     let mut pos = 12usize;
     while pos + 8 <= bytes.len() {
         let id = &bytes[pos..pos + 4];
-        let size = u32::from_le_bytes([bytes[pos + 4], bytes[pos + 5], bytes[pos + 6], bytes[pos + 7]]) as usize;
+        let size = u32::from_le_bytes([
+            bytes[pos + 4],
+            bytes[pos + 5],
+            bytes[pos + 6],
+            bytes[pos + 7],
+        ]) as usize;
         let body_start = pos + 8;
         let body_end = (body_start + size).min(bytes.len());
         match id {
@@ -45,7 +50,9 @@ pub fn read(path: &Path) -> Result<WavData, String> {
                 sample_rate = u32::from_le_bytes([fmt[4], fmt[5], fmt[6], fmt[7]]);
                 bits = u16::from_le_bytes([fmt[14], fmt[15]]);
                 if audio_format != 1 {
-                    return Err(format!("unsupported WAV format tag {audio_format} (need PCM=1)"));
+                    return Err(format!(
+                        "unsupported WAV format tag {audio_format} (need PCM=1)"
+                    ));
                 }
             }
             b"data" => {
@@ -75,7 +82,10 @@ pub fn read(path: &Path) -> Result<WavData, String> {
         samples.push(avg / 32768.0);
     }
 
-    Ok(WavData { samples, sample_rate })
+    Ok(WavData {
+        samples,
+        sample_rate,
+    })
 }
 
 /// Writes mono `f32` samples (clamped to `[-1, 1]`) as a 16-bit PCM WAV. Used by