Guard browser storage behind OPFS

docs/linuxcnc-source-policy.md

@@ -16,6 +16,10 @@ Hard rules:
   LinuxCNC source before implementation.
 - Browser-side wasm filesystem behavior must use OPFS-backed storage. Do not
   add browser filesystem paths that bypass OPFS.
+- Browser app and wasm bridge code must not persist CNC programs, LinuxCNC
+  parameter files, or mirrored workspace files through non-OPFS browser storage
+  APIs such as Local Storage, IndexedDB, File Picker writes, WebKit filesystem
+  APIs, or FileReader-backed import paths.
 
 Allowed project code:
 
@@ -61,6 +65,8 @@ Efficiency rules:
   permission to expand the pass into another workstream.
 - Do not add a smoke-only behavior path when the LinuxCNC-backed route already
   exists; add coverage to the source-backed route instead.
+- Keep browser filesystem guardrails negative as well as positive: require the
+  OPFS bridge and reject browser app/wasm storage APIs that could bypass it.
 - Smoke tests are verification guardrails. They must not be expanded with new
   functional CNC behavior unless that behavior is directly routed to, copied
   from, or checked against the relevant LinuxCNC source in the same narrow