Fix Linux debug builds: use production deps path, improve signal reporting

- dependency_locator: Skip upward deps/ search on Linux since deps are
  always installed to ~/.local/share/VapourBox/deps/. The upward search
  was matching macOS deps/ and generating invalid env vars. Keep the old
  behaviour for macOS/Windows debug builds.
- pipeline_executor: Report actual signal name (e.g. SIGSEGV) instead of
  opaque exit code -1 when a process is killed by a signal.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: StuartCameronCode

worker/src/dependency_locator.rs

@@ -33,11 +33,13 @@ impl DependencyLocator {
     }
 
     /// Find the deps directory by searching various locations.
-    fn find_deps_directory(exe_path: &Path) -> Result<PathBuf> {
-        // Development only: search upward from executable for project deps.
+    fn find_deps_directory(#[allow(unused)] exe_path: &Path) -> Result<PathBuf> {
+        // Development only (macOS/Windows): search upward from executable for project deps.
         // This is restricted to debug builds for security - release builds
         // should only check known production paths.
-        #[cfg(debug_assertions)]
+        // Linux always uses the production path since deps are built/downloaded
+        // separately and installed to ~/.local/share/VapourBox/deps/.
+        #[cfg(all(debug_assertions, not(target_os = "linux")))]
         {
             let mut current = exe_path.parent();
             while let Some(dir) = current {
@@ -47,9 +49,7 @@ impl DependencyLocator {
                     // to distinguish from Cargo's deps folder.
                     let has_platform_dir = deps_dir.join("windows-x64").exists()
                         || deps_dir.join("macos-arm64").exists()
-                        || deps_dir.join("macos-x64").exists()
-                        || deps_dir.join("linux-x64").exists()
-                        || deps_dir.join("linux-arm64").exists();
+                        || deps_dir.join("macos-x64").exists();
                     if has_platform_dir {
                         return Ok(deps_dir);
                     }

worker/src/pipeline_executor.rs

@@ -9,8 +9,35 @@ use std::sync::Arc;
 use std::thread;
 use std::time::Duration;
 
+#[cfg(unix)]
+use std::os::unix::process::ExitStatusExt;
+
 use anyhow::{bail, Context, Result};
 
+/// Format an exit status for error messages, including signal info on Unix.
+fn format_exit_status(status: &std::process::ExitStatus) -> String {
+    if let Some(code) = status.code() {
+        return format!("exit code {}", code);
+    }
+    #[cfg(unix)]
+    {
+        if let Some(sig) = status.signal() {
+            let name = match sig {
+                1 => "SIGHUP",
+                2 => "SIGINT",
+                6 => "SIGABRT",
+                9 => "SIGKILL",
+                11 => "SIGSEGV",
+                13 => "SIGPIPE",
+                15 => "SIGTERM",
+                _ => "unknown",
+            };
+            return format!("signal {} ({})", sig, name);
+        }
+    }
+    "unknown status".to_string()
+}
+
 use crate::dependency_locator::DependencyLocator;
 use crate::models::{AudioMode, ContainerFormat, DeinterlaceMethod, EncoderFamily, EncodingSettings, LogLevel, ProgressInfo, SubtitleOutput, VideoCodec, VideoJob};
 use crate::progress_reporter::ProgressReporter;
@@ -370,21 +397,21 @@ impl PipelineExecutor {
         if let Some(status) = decoder_status {
             let code = status.code().unwrap_or(-1);
             if code != 0 && code != 130 && code != 141 && code != 224 {
-                bail!("Decoder ffmpeg exited with code {}", code);
+                bail!("Decoder ffmpeg exited with {}", format_exit_status(&status));
             }
         }
 
         if let Some(status) = vspipe_status {
             let code = status.code().unwrap_or(-1);
             if code != 0 && code != 130 && code != 141 {
-                bail!("vspipe exited with code {}", code);
+                bail!("vspipe exited with {}", format_exit_status(&status));
             }
         }
 
         let ffmpeg_ok = if let Some(status) = ffmpeg_status {
             let code = status.code().unwrap_or(-1);
             if code != 0 && code != 130 && code != 141 {
-                bail!("ffmpeg exited with code {}", code);
+                bail!("ffmpeg exited with {}", format_exit_status(&status));
             }
             true
         } else {
@@ -790,11 +817,11 @@ impl PipelineExecutor {
             if !errors.is_empty() {
                 bail!("vspipe failed: {}", errors.join("\n"));
             }
-            bail!("vspipe exited with code {}", vspipe_status.code().unwrap_or(-1));
+            bail!("vspipe exited with {}", format_exit_status(&vspipe_status));
         }
 
         if !output.status.success() {
-            bail!("ffmpeg encoder exited with code {}", output.status.code().unwrap_or(-1));
+            bail!("ffmpeg encoder exited with {}", format_exit_status(&output.status));
         }
 
         // Write PNG to stdout