fc-common: add failed paths cache infrastructure

Signed-off-by: NotAShelf <raf@notashelf.dev>
Change-Id: I35f9bfb044160151cf73c43ed9ada3476a6a6964

crates/common/src/config.rs

@@ -79,6 +79,14 @@ pub struct QueueRunnerConfig {
   /// retrying.
   #[serde(default)]
   pub strict_errors: bool,
+
+  /// Cache failed derivation paths to skip known-failing builds.
+  #[serde(default = "default_true")]
+  pub failed_paths_cache: bool,
+
+  /// TTL in seconds for failed paths cache entries (default 24h).
+  #[serde(default = "default_failed_paths_ttl")]
+  pub failed_paths_ttl: u64,
 }
 
 #[derive(Debug, Clone, Serialize, Deserialize)]
@@ -405,6 +413,10 @@ const fn default_true() -> bool {
   true
 }
 
+const fn default_failed_paths_ttl() -> u64 {
+  86400
+}
+
 const fn default_check_interval() -> i32 {
   60
 }
@@ -521,11 +533,13 @@ impl Default for EvaluatorConfig {
 impl Default for QueueRunnerConfig {
   fn default() -> Self {
     Self {
-      workers:       4,
-      poll_interval: 5,
-      build_timeout: 3600,
-      work_dir:      PathBuf::from("/tmp/fc-queue-runner"),
-      strict_errors: false,
+      workers:            4,
+      poll_interval:      5,
+      build_timeout:      3600,
+      work_dir:           PathBuf::from("/tmp/fc-queue-runner"),
+      strict_errors:      false,
+      failed_paths_cache: true,
+      failed_paths_ttl:   86400,
     }
   }
 }