huskies: merge 1199 story Orphaned build-dir GC: reclaim dead worktree targets without touching warm caches

server/src/config/mod.rs

@@ -148,6 +148,13 @@ pub struct ProjectConfig {
     /// merge or `FixupRequested`).  Default: 3.  Set to 0 to disable.
     #[serde(default = "default_merge_failure_block_threshold")]
     pub merge_failure_block_threshold: u32,
+    /// Free space (in GB) below which an automatic build-directory GC pass
+    /// (story 1199) is triggered to reclaim orphaned worktree `target/` dirs
+    /// and a stale `.huskies/merge_workspace`. Checked on the same tick as the
+    /// low-disk watchdog (story 1200), not a separate timer. Default: 0
+    /// (disabled) — the on-demand `gc` MCP tool remains available regardless.
+    #[serde(default)]
+    pub gc_min_free_gb: u64,
 }
 
 /// Configuration for the filesystem watcher's sweep behaviour.
@@ -464,6 +471,7 @@ impl Default for ProjectConfig {
             gateway_project: None,
             status_push_enabled: default_status_push_enabled(),
             merge_failure_block_threshold: default_merge_failure_block_threshold(),
+            gc_min_free_gb: 0,
         }
     }
 }
@@ -555,6 +563,7 @@ impl ProjectConfig {
                         gateway_project: None,
                         status_push_enabled: default_status_push_enabled(),
                         merge_failure_block_threshold: default_merge_failure_block_threshold(),
+                        gc_min_free_gb: 0,
                     };
                     validate_agents(&config.agent)?;
                     return Ok(config);
@@ -597,6 +606,7 @@ impl ProjectConfig {
                         gateway_project: None,
                         status_push_enabled: default_status_push_enabled(),
                         merge_failure_block_threshold: default_merge_failure_block_threshold(),
+                        gc_min_free_gb: 0,
                     };
                     validate_agents(&config.agent)?;
                     Ok(config)
@@ -627,6 +637,7 @@ impl ProjectConfig {
                         gateway_project: None,
                         status_push_enabled: default_status_push_enabled(),
                         merge_failure_block_threshold: default_merge_failure_block_threshold(),
+                        gc_min_free_gb: 0,
                     })
                 }
             }