✨ feat: add self-update capability

Add `tmuxido --update` command to update binary from latest release.
- New `self_update` module with version comparison
- Atomic binary replacement with backup/rollback
- Fetches latest release from Gitea API
- Downloads correct binary for system architecture

src/self_update.rs

@@ -0,0 +1,218 @@
+use anyhow::{Context, Result};
+use std::os::unix::fs::PermissionsExt;
+use std::path::PathBuf;
+use std::process::Command;
+
+const REPO: &str = "cinco/Tmuxido";
+const BASE_URL: &str = "https://git.cincoeuzebio.com";
+
+/// Check if running from cargo (development mode)
+fn is_dev_build() -> bool {
+    option_env!("CARGO_PKG_NAME").is_none()
+}
+
+/// Get current version from cargo
+pub fn current_version() -> &'static str {
+    env!("CARGO_PKG_VERSION")
+}
+
+/// Detect system architecture
+fn detect_arch() -> Result<&'static str> {
+    let arch = std::env::consts::ARCH;
+    match arch {
+        "x86_64" => Ok("x86_64-linux"),
+        "aarch64" => Ok("aarch64-linux"),
+        _ => Err(anyhow::anyhow!("Unsupported architecture: {}", arch)),
+    }
+}
+
+/// Fetch latest release tag from Gitea API
+fn fetch_latest_tag() -> Result<String> {
+    let url = format!("{}/api/v1/repos/{}/releases?limit=1&page=1", BASE_URL, REPO);
+
+    let output = Command::new("curl")
+        .args(["-fsSL", &url])
+        .output()
+        .context("Failed to execute curl. Make sure curl is installed.")?;
+
+    if !output.status.success() {
+        return Err(anyhow::anyhow!(
+            "Failed to fetch latest release: {}",
+            String::from_utf8_lossy(&output.stderr)
+        ));
+    }
+
+    let response = String::from_utf8_lossy(&output.stdout);
+
+    // Parse JSON response to extract tag_name
+    let tag: serde_json::Value =
+        serde_json::from_str(&response).context("Failed to parse release API response")?;
+
+    tag.get(0)
+        .and_then(|r| r.get("tag_name"))
+        .and_then(|t| t.as_str())
+        .map(|t| t.to_string())
+        .ok_or_else(|| anyhow::anyhow!("Could not extract tag_name from release"))
+}
+
+/// Get path to current executable
+fn get_current_exe() -> Result<PathBuf> {
+    std::env::current_exe().context("Failed to get current executable path")
+}
+
+/// Download binary to a temporary location
+fn download_binary(tag: &str, arch: &str, temp_path: &std::path::Path) -> Result<()> {
+    let url = format!("{}/{}/releases/download/{}/{}", BASE_URL, REPO, tag, arch);
+
+    println!("Downloading {}...", url);
+
+    let output = Command::new("curl")
+        .args(["-fsSL", &url, "-o", &temp_path.to_string_lossy()])
+        .output()
+        .context("Failed to execute curl for download")?;
+
+    if !output.status.success() {
+        return Err(anyhow::anyhow!(
+            "Failed to download binary: {}",
+            String::from_utf8_lossy(&output.stderr)
+        ));
+    }
+
+    // Make executable
+    let mut perms = std::fs::metadata(temp_path)?.permissions();
+    perms.set_mode(0o755);
+    std::fs::set_permissions(temp_path, perms)?;
+
+    Ok(())
+}
+
+/// Perform self-update
+pub fn self_update() -> Result<()> {
+    if is_dev_build() {
+        println!("Development build detected. Skipping self-update.");
+        return Ok(());
+    }
+
+    let current = current_version();
+    println!("Current version: {}", current);
+
+    let latest = fetch_latest_tag()?;
+    let latest_clean = latest.trim_start_matches('v');
+    println!("Latest version: {}", latest);
+
+    // Compare versions (simple string comparison for semver without 'v' prefix)
+    if latest_clean == current {
+        println!("Already up to date!");
+        return Ok(());
+    }
+
+    // Check if latest is actually newer
+    match version_compare(latest_clean, current) {
+        std::cmp::Ordering::Less => {
+            println!("Current version is newer than release. Skipping update.");
+            return Ok(());
+        }
+        std::cmp::Ordering::Equal => {
+            println!("Already up to date!");
+            return Ok(());
+        }
+        _ => {}
+    }
+
+    let arch = detect_arch()?;
+    let exe_path = get_current_exe()?;
+
+    // Create temporary file in same directory as target (for atomic rename)
+    let exe_dir = exe_path
+        .parent()
+        .ok_or_else(|| anyhow::anyhow!("Could not determine executable directory"))?;
+    let temp_path = exe_dir.join(".tmuxido.new");
+
+    println!("Downloading update...");
+    download_binary(&latest, arch, &temp_path)?;
+
+    // Verify the downloaded binary works
+    let verify = Command::new(&temp_path).arg("--version").output();
+    if let Err(e) = verify {
+        let _ = std::fs::remove_file(&temp_path);
+        return Err(anyhow::anyhow!(
+            "Downloaded binary verification failed: {}",
+            e
+        ));
+    }
+
+    // Atomic replace: rename old to .old, rename new to target
+    let backup_path = exe_path.with_extension("old");
+
+    // Remove old backup if exists
+    let _ = std::fs::remove_file(&backup_path);
+
+    // Rename current to backup
+    std::fs::rename(&exe_path, &backup_path)
+        .context("Failed to backup current binary (is tmuxido running?)")?;
+
+    // Move new to current location
+    if let Err(e) = std::fs::rename(&temp_path, &exe_path) {
+        // Restore backup on failure
+        let _ = std::fs::rename(&backup_path, &exe_path);
+        return Err(anyhow::anyhow!("Failed to install new binary: {}", e));
+    }
+
+    // Remove backup on success
+    let _ = std::fs::remove_file(&backup_path);
+
+    println!("Successfully updated to {}!", latest);
+    Ok(())
+}
+
+/// Compare two semver versions
+fn version_compare(a: &str, b: &str) -> std::cmp::Ordering {
+    let parse = |s: &str| {
+        s.split('.')
+            .filter_map(|n| n.parse::<u32>().ok())
+            .collect::<Vec<_>>()
+    };
+
+    let a_parts = parse(a);
+    let b_parts = parse(b);
+
+    for (a_part, b_part) in a_parts.iter().zip(b_parts.iter()) {
+        match a_part.cmp(b_part) {
+            std::cmp::Ordering::Equal => continue,
+            other => return other,
+        }
+    }
+
+    a_parts.len().cmp(&b_parts.len())
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn should_detect_current_version() {
+        let version = current_version();
+        // Version should be non-empty and contain dots
+        assert!(!version.is_empty());
+        assert!(version.contains('.'));
+    }
+
+    #[test]
+    fn should_compare_versions_correctly() {
+        assert_eq!(
+            version_compare("0.3.0", "0.2.4"),
+            std::cmp::Ordering::Greater
+        );
+        assert_eq!(version_compare("0.2.4", "0.3.0"), std::cmp::Ordering::Less);
+        assert_eq!(version_compare("0.3.0", "0.3.0"), std::cmp::Ordering::Equal);
+        assert_eq!(
+            version_compare("1.0.0", "0.9.9"),
+            std::cmp::Ordering::Greater
+        );
+        assert_eq!(
+            version_compare("0.10.0", "0.9.0"),
+            std::cmp::Ordering::Greater
+        );
+    }
+}