test scripts: known-file picker for the file actions

The UPDATE file / READ file step editor's path field gains the selector
the APDU builder's SELECT rows use: the loaded file-manager tree, the
custom files and the standard uicc_files.json list, merged by
rfmFileEntries, grouped by root with a filter.  Picking a file fills
test-f-path; the text field stays authoritative (a name path or an
unlisted file can still be typed) and the current path is preselected
when known.  Only EFs are offered - the action reads/writes a file, so a
DF/ADF is not a target.

v3.38.0: server.py VERSION, pyproject.toml and the PWA header;
sw cache simple-v478 (help/index changed); a CHANGELOG [3.38.0] section,
the help EN/RU, docs/test-scripts.md and the AGENTS notes.

Tests: frontend/tests/testscripts.test.js - the option list/grouping, the
EF-only filter, the filter input, the pick->path fill and the form's
picker render for write and read.  1061 Python + 1071 frontend.

docs/test-scripts.md

@@ -329,7 +329,12 @@ consecutive runs continue correctly.
 | `proactive-drain` | `respond`, `first`, `attempts` 1–1000 (default 3), `interval_ms` (default 200), `require` | drain the card's announced proactive commands and confirm it is idle (see below) |
 
 `path` is `/`-separated: `MF` (or `3F00`) or an ADF name/AID first, then FIDs
-or file names - e.g. `MF/7F20/6F07`, `ADF.USIM/EF.TEST`.
+or file names - e.g. `MF/7F20/6F07`, `ADF.USIM/EF.TEST`.  The step editor's
+**pick a known file** selector (the same source merge as the APDU builder's
+SELECT picker: the loaded file tree, custom files and the standard
+`uicc_files.json` list, grouped by root, with a filter) fills the path;
+only EFs are listed, and the text field stays authoritative (typing a name
+path or an unlisted file is always possible).
 
 `file-write` sends a direct terminal-side UPDATE BINARY/RECORD - it does **not**
 fire the card's EVENT_REMOTE_FILE_UPDATE (that event reports an update done by