尽快推进：收紧OPFS程序读取源码锚点

docs/linuxcnc-opfs-source-map.md

@@ -11,6 +11,9 @@ persistence. It is a policy and bridge map only; it must not add independent fil
   `RS274NGC_PARAMETER_FILE_BACKUP_SUFFIX` as `.bak`.
 - `src/emc/rs274ngc/rs274ngc_pre.cc` implements
   `Interp::restore_parameters()` for parameter-file reads.
+- `src/emc/rs274ngc/rs274ngc_pre.cc` implements `Interp::open()` by opening
+  the NC program file with `fopen(filename, "r")`, then `Interp::_read()`
+  feeds `_setup.file_pointer` into `read_text()`.
 - `src/emc/rs274ngc/rs274ngc_pre.cc` implements
   `Interp::save_parameters()` for `filename + ".new"`, backup, and replacement
   writes.
@@ -22,7 +25,7 @@ persistence. It is a policy and bridge map only; it must not add independent fil
 
 | Entry | Boundary |
 | --- | --- |
-| `web/src/wasm-core.js` | Keeps LinuxCNC parameter restore/save bridge files under the OPFS workspace and cleans WASM scratch files. |
+| `web/src/wasm-core.js` | Keeps LinuxCNC program reads and parameter restore/save bridge files under the OPFS workspace and cleans WASM scratch files. |
 | `web/src/wasm-core.d.ts` | Exposes only the OPFS-backed workspace, directory, parameter-file, and mount/workspace option types used by the bridge. |
 | `web/src/app.js` | Persists browser programs at `programs/current.ngc` and LinuxCNC parameters at `parameters/rs274ngc.var`. |
 | `web/test-browser-wasm-smoke-opfs-basic-sections.js` | Verifies OPFS program file reads through LinuxCNC `read_text()` and rejects unsafe paths. |