feat: add --header / -H flag for custom HTTP headers in fetch command

Allows passing arbitrary HTTP headers to fetch requests, enabling:
- Authorization: Bearer tokens for authenticated APIs like SOM Cache
- Custom headers for sites that require specific request headers
- Multiple headers via repeated --header flags

Examples:
  plasmate fetch https://cache.plasmate.app/v1/som?url=... -H 'Authorization: Bearer sk-...'
  plasmate fetch https://example.com -H 'X-Custom: value' -H 'Accept-Language: en'

The flag is available as --header or -H (matching curl convention).
Internally adds build_client_h1_fallback_with_headers() to the network layer.

Author: dbhurley

src/main.rs

@@ -137,6 +137,15 @@ enum Commands {
         /// Disable JavaScript execution entirely
         #[arg(long)]
         no_js: bool,
+        /// Add custom HTTP headers (can be specified multiple times).
+        ///
+        /// Format: "Header-Name: value"
+        ///
+        /// Examples:
+        ///   --header "Authorization: Bearer sk-..."
+        ///   --header "X-Custom: value" --header "Accept-Language: en"
+        #[arg(long, short = 'H')]
+        header: Vec<String>,
         /// Load cookies from a stored auth profile (domain name)
         #[arg(long)]
         profile: Option<String>,
@@ -391,6 +400,7 @@ async fn main() -> Result<(), Box<dyn std::error::Error>> {
             timeout,
             no_external,
             no_js,
+            header,
             profile,
             tls,
             plugin: plugin_paths,
@@ -405,6 +415,8 @@ async fn main() -> Result<(), Box<dyn std::error::Error>> {
                 network::tls::set_global(tls_config);
             }
             let mut plugins = load_plugins(&plugin_paths)?;
+            // Parse custom headers
+            let extra_headers = parse_header_args(&header);
             cmd_fetch(
                 &url,
                 output.as_deref(),
@@ -415,6 +427,7 @@ async fn main() -> Result<(), Box<dyn std::error::Error>> {
                 !no_external,
                 no_js,
                 profile.as_deref(),
+                &extra_headers,
                 plugins.as_mut(),
             )
             .await?;
@@ -993,6 +1006,23 @@ fn load_plugins(
     Ok(Some(pm))
 }
 
+/// Parse `--header "Key: Value"` arguments into a `HashMap`.
+fn parse_header_args(args: &[String]) -> std::collections::HashMap<String, String> {
+    let mut map = std::collections::HashMap::new();
+    for arg in args {
+        if let Some(pos) = arg.find(':') {
+            let key = arg[..pos].trim().to_string();
+            let val = arg[pos + 1..].trim().to_string();
+            if !key.is_empty() {
+                map.insert(key, val);
+            }
+        } else {
+            eprintln!("Warning: ignoring malformed header (expected 'Name: value'): {}", arg);
+        }
+    }
+    map
+}
+
 async fn cmd_fetch(
     url: &str,
     output: Option<&str>,
@@ -1003,6 +1033,7 @@ async fn cmd_fetch(
     external_scripts: bool,
     no_js: bool,
     profile: Option<&str>,
+    extra_headers: &std::collections::HashMap<String, String>,
     mut plugins: Option<&mut plugin::PluginManager>,
 ) -> Result<(), Box<dyn std::error::Error>> {
     // Check if the daemon is running and delegate to it
@@ -1040,7 +1071,8 @@ async fn cmd_fetch(
     }
 
     let tls_config = network::tls::global();
-    let client = network::fetch::build_client_h1_fallback(user_agent, jar, tls_config)?;
+    let headers_opt = if extra_headers.is_empty() { None } else { Some(extra_headers) };
+    let client = network::fetch::build_client_h1_fallback_with_headers(user_agent, jar, tls_config, headers_opt)?;
 
     // Plugin hook: pre_navigate
     let effective_url = if let Some(pm) = plugins.as_deref_mut() {

src/network/fetch.rs

@@ -76,8 +76,31 @@ pub fn build_client_h1_fallback(
     cookie_jar: Arc<Jar>,
     tls_config: Option<&TlsConfig>,
 ) -> Result<Client, FetchError> {
+    build_client_h1_fallback_with_headers(user_agent, cookie_jar, tls_config, None)
+}
+
+/// Build an HTTP/1.1 client with optional extra default headers.
+pub fn build_client_h1_fallback_with_headers(
+    user_agent: Option<&str>,
+    cookie_jar: Arc<Jar>,
+    tls_config: Option<&TlsConfig>,
+    extra_headers: Option<&std::collections::HashMap<String, String>>,
+) -> Result<Client, FetchError> {
+    let mut headers = reqwest::header::HeaderMap::new();
+    if let Some(eh) = extra_headers {
+        for (k, v) in eh {
+            if let (Ok(name), Ok(val)) = (
+                reqwest::header::HeaderName::from_bytes(k.as_bytes()),
+                reqwest::header::HeaderValue::from_str(v),
+            ) {
+                headers.insert(name, val);
+            }
+        }
+    }
+
     let mut builder = Client::builder()
         .user_agent(user_agent.unwrap_or(DEFAULT_USER_AGENT))
+        .default_headers(headers)
         .cookie_provider(cookie_jar)
         .redirect(reqwest::redirect::Policy::limited(10))
         .pool_max_idle_per_host(16)