Monitor only the active project file

Watching referenced and inactive projects can produce reload prompts outside the current document. Register watches only when a project becomes active, and retain content baselines so unchanged writes and application saves stay quiet.

Debounce file and directory events, retry transient read failures, and restore monitoring after replacement or deletion and recreation. Validate reload ownership around the dialog and scope candidate projects so failed reloads release their resources. Check read errors before clearing existing model data.

docs/asset-loading.md

@@ -107,6 +107,26 @@ and project teardown unregister borrowed index entries; they must not leave
 lookup pointers to deleted objects. These paths are in
 [project.cpp](../common/project.cpp) and [lc_model.cpp](../common/lc_model.cpp).
 
+### Active project file monitoring
+
+Only the active project's own file is watched. Preview projects, loading
+candidates, and referenced model projects do not register filesystem watches.
+`lcApplication::SetProject()` activates the new project's watcher after changing
+the active project. Loaded bytes and committed saves establish its content hash
+baseline, so unchanged rewrites, metadata updates, and own saves do not prompt.
+
+File and containing-directory events are debounced before checking the active
+file's contents, existence, and readability. Directory watches reattach after
+replacement and detect deletion/recreation, including missing parent directories.
+Transient read failures receive bounded retries. Events for unrelated files in
+the directory only cause the current file to be checked.
+
+The reload handler verifies the active project and filename before showing a
+dialog and after the response. Candidate ownership is scoped so failed reloads
+release their resources. Referenced files retain their existing loading and
+readiness policies and are not monitored or reloaded in response to filesystem
+events.
+
 ## Readiness
 
 ```mermaid