feat: publish-ready overhaul — lints, tests, docs, CI, fuzzing, mutant testing

- Enable clippy pedantic + nursery lints; fix all warnings
- Add config validation (SF, CR, frequency range checks)
- Zeroize passphrase intermediates after key derivation
- Convert to lib+bin crate for fuzz target accessibility
- Replace Vec with VecDeque for O(1) log/bucket rotation
- Add TUI minimum terminal size guard

Testing:
- 145 unit + property tests (was 15)
- 6 proptest groups (frame roundtrip, hash, SNR, air time, peer list, padding)
- 2 cargo-fuzz targets (gossip frame decode, peer list decode)
- cargo-mutants: 0 missed, 241 caught, 54 unviable

Documentation:
- README with prerequisites, quick start, config reference, architecture
- Module-level and item-level rustdoc on all public items
- LICENSE (MIT), rustfmt.toml, .gitignore

Infrastructure:
- GitHub Actions CI (fmt, clippy, test, audit)
- cargo-mutants config (.cargo/mutants.toml)
- justfile for common tasks

src/setup.rs

@@ -17,10 +17,8 @@ const RESET: &str = "\x1b[0m";
 
 /// Run the interactive setup wizard. If `existing` is Some, use those values as defaults.
 pub fn run_wizard(config_path: &Path, existing: Option<&Config>) -> Result<()> {
-    let defaults = existing.map_or_else(
-        || (RadioSection::default(), BridgeSection::default()),
-        |c| (c.radio.clone(), c.bridge.clone()),
-    );
+    let defaults = existing
+        .map_or_else(|| (RadioSection::default(), BridgeSection::default()), |c| (c.radio.clone(), c.bridge.clone()));
     let (radio, bridge) = defaults;
 
     println!();
@@ -43,8 +41,9 @@ pub fn run_wizard(config_path: &Path, existing: Option<&Config>) -> Result<()> {
 
     // ── Radio ────────────────────────────────────────────────────
 
-    let freq_default = format!("{:.3}", radio.frequency as f64 / 1_000_000.0);
+    let freq_default = format!("{:.3}", f64::from(radio.frequency) / 1_000_000.0);
     let freq_mhz: f64 = prompt_parse("Frequency (MHz)", &freq_default)?;
+    #[allow(clippy::cast_possible_truncation, clippy::cast_sign_loss)] // validated by prompt_parse
     let frequency = (freq_mhz * 1_000_000.0) as u32;
 
     let bandwidth = prompt_default("Bandwidth", &radio.bandwidth)?;
@@ -70,11 +69,7 @@ pub fn run_wizard(config_path: &Path, existing: Option<&Config>) -> Result<()> {
 
     let port_default = radio.port.as_deref().unwrap_or("auto");
     let port_str = prompt_default("Serial Port", port_default)?;
-    let port = if port_str == "auto" || port_str.is_empty() {
-        None
-    } else {
-        Some(port_str)
-    };
+    let port = if port_str == "auto" || port_str.is_empty() { None } else { Some(port_str) };
 
     // ── Build and save ───────────────────────────────────────────
 
@@ -111,12 +106,10 @@ pub fn run_wizard(config_path: &Path, existing: Option<&Config>) -> Result<()> {
 
 fn write_config(path: &Path, cfg: &Config) -> Result<()> {
     if let Some(parent) = path.parent() {
-        std::fs::create_dir_all(parent)
-            .with_context(|| format!("creating directory: {}", parent.display()))?;
+        std::fs::create_dir_all(parent).with_context(|| format!("creating directory: {}", parent.display()))?;
     }
     let content = toml::to_string_pretty(cfg).context("serializing config")?;
-    std::fs::write(path, content)
-        .with_context(|| format!("writing config: {}", path.display()))?;
+    std::fs::write(path, content).with_context(|| format!("writing config: {}", path.display()))?;
     Ok(())
 }
 
@@ -128,20 +121,12 @@ fn prompt_default(label: &str, default: &str) -> Result<String> {
     let mut input = String::new();
     io::stdin().read_line(&mut input)?;
     let trimmed = input.trim();
-    if trimmed.is_empty() {
-        Ok(default.to_string())
-    } else {
-        Ok(trimmed.to_string())
-    }
+    if trimmed.is_empty() { Ok(default.to_string()) } else { Ok(trimmed.to_string()) }
 }
 
 fn prompt_required(label: &str, default: Option<&str>) -> Result<String> {
     loop {
-        let prompt = if let Some(d) = default {
-            format!("  {label} {DIM}[{d}]{RESET}: ")
-        } else {
-            format!("  {label}: ")
-        };
+        let prompt = default.map_or_else(|| format!("  {label}: "), |d| format!("  {label} {DIM}[{d}]{RESET}: "));
         print!("{prompt}");
         io::stdout().flush()?;
         let mut input = String::new();
@@ -175,3 +160,35 @@ fn parse_sync_word(s: &str) -> Result<u16> {
     let s = s.strip_prefix("0x").unwrap_or(&s);
     u16::from_str_radix(s, 16).with_context(|| format!("invalid sync word: {s}"))
 }
+
+#[cfg(test)]
+#[allow(clippy::unwrap_used, clippy::expect_used)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn parse_sync_word_hex_prefix() {
+        assert_eq!(parse_sync_word("0x3444").unwrap(), 0x3444);
+    }
+
+    #[test]
+    fn parse_sync_word_no_prefix() {
+        assert_eq!(parse_sync_word("3444").unwrap(), 0x3444);
+    }
+
+    #[test]
+    fn parse_sync_word_case_insensitive() {
+        assert_eq!(parse_sync_word("0xABCD").unwrap(), 0xABCD);
+    }
+
+    #[test]
+    fn parse_sync_word_whitespace() {
+        assert_eq!(parse_sync_word("  0x3444  ").unwrap(), 0x3444);
+    }
+
+    #[test]
+    fn parse_sync_word_invalid() {
+        assert!(parse_sync_word("ZZZZ").is_err());
+        assert!(parse_sync_word("").is_err());
+    }
+}