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

server/src/startup/tick_loop.rs

@@ -241,6 +241,45 @@ pub(crate) fn spawn_tick_loop(
                     &disk_watch_status,
                     &disk_watch_host_id,
                 );
+
+                // Orphaned build-dir GC (story 1199): tied to the same
+                // low-disk signal as the watchdog above rather than its own
+                // timer. `gc_min_free_gb == 0` (default) disables this —
+                // the on-demand `gc` MCP tool remains available regardless.
+                let gc_min_free_gb = config::ProjectConfig::load(r)
+                    .map(|c| c.gc_min_free_gb)
+                    .unwrap_or(0);
+                if let Ok(free_bytes) = service::disk_watch::io::free_space_bytes(r)
+                    && service::gc::should_auto_run(gc_min_free_gb, free_bytes)
+                {
+                    let gc_root = r.clone();
+                    tokio::spawn(async move {
+                        service::gc::io::run_gc_pass(&gc_root).await;
+                    });
+                }
+            }
+
+            // Orphaned build-dir GC (story 1199): if free disk falls below
+            // `gc_min_free_gb`, run a GC pass to reclaim orphaned worktree
+            // `target/` dirs and a stale `merge_workspace`. Checked on the
+            // same disk-space tick as the low-disk watchdog above — not a
+            // separate timer — so GC only ever runs in response to an actual
+            // low-disk condition. `gc_min_free_gb` absent or 0 disables this
+            // (the on-demand `gc` MCP tool still works).
+            if tick_count.is_multiple_of(30)
+                && let Some(ref r) = root
+            {
+                let gc_min_free_gb = config::ProjectConfig::load(r)
+                    .map(|c| c.gc_min_free_gb)
+                    .unwrap_or(0);
+                if let Ok(free_bytes) = service::disk_watch::io::free_space_bytes(r)
+                    && service::gc::should_auto_run(gc_min_free_gb, free_bytes)
+                {
+                    let root_for_gc = r.clone();
+                    tokio::spawn(async move {
+                        service::gc::io::run_gc_pass(&root_for_gc).await;
+                    });
+                }
             }
 
             // Periodic reconciler: converge subscriber side effects so that