Command filter: FETCH and TERMINAL RESPONSE are separate entries (v2.7.1)

- the old "FETCH: ANY PROACTIVE" grouping label is gone: filter_label() now
  gives every command its own label, so the menu lists FETCH and TERMINAL
  RESPONSE individually — the multi-select filter (and the presets) cover the
  combinations that the grouping used to bundle
- the proactive presets keep their meaning: they name FETCH and TERMINAL
  PROFILE and reach the rest (a TERMINAL RESPONSE included) through the SW
  91xx rule; selecting FETCH now also brings its GET RESPONSE, which carries
  the fetched proactive command
- tests: the proactive-preset case follows the split (a TERMINAL RESPONSE is
  covered by 91xx, not by its name) plus a new case pinning the separate
  labels and the FETCH/GR pairing; 527 Python + 73 Node tests
- PWA_VERSION/pyproject/version.py 2.7.1, SW cache simtrace-analyser-v81

frontend/sw.js

@@ -1,4 +1,4 @@
-const CACHE = 'simtrace-analyser-v80';
+const CACHE = 'simtrace-analyser-v81';
 
 const PRECACHE = [
     'index.html',