website: M3 part A - the controller's shell, and the home page inside it

The direction the operator chose: the controller's FRAME around the website's own
content. Staged at /preview/m3/, noindex, nothing live.

website/assets/shell.css - 117 rules COPIED VERBATIM from felhom-controller
  style.css @ dcd89364a4 (sidebar, mobile top bar, off-canvas drawer, and the
  component atoms the restyled pages use: btn, alert, app-info-card, launch-*,
  stack-detail-card, form-*). Exactly ONE rule is not verbatim and says so:
  body.shell { display:flex; min-height:100vh }, which lives in the controller's
  base rather than in a component, scoped to .shell so other pages are untouched.

  The generator NAMES every rule it copies and REFUSES to write the file if one has
  disappeared upstream. That is not ceremony: it already caught two things this
  session. It refused because .sidebar::-webkit-scrollbar does not exist (only the
  -track override does), and because prefers-reduced-motion is split across FIVE
  separate blocks in the controller - reading only the first would have silently
  lost four rules. The M1 round lost a rule exactly this way.

  The bare `body { flex-direction: column }` that broke M1's phone layout is copied
  this time, by name, as are body.nav-open and the no-js/js pair.

  Load order is deliberate: shell.css AFTER site.css. Thirteen selectors exist in
  both files with different meanings (.nav-links, .page-header, .lang-globe*, .ico)
  - a horizontal site nav there, a vertical sidebar here. Later wins, and a page
  that does not load shell.css is completely unaffected.

website/preview/m3/index.html - the home page in the shell. Content is /preview/'s
  cleaned text; body carries `shell page-index` so the existing .page-index content
  rules (caps, flow, vs, band, who-mini) are reused rather than duplicated. Six
  sections, left-aligned headers, the controller's cards. Head tags (title, meta
  description, canonical, hreflang) are already the FINAL values, so the switch in
  part D needs no head edit.

  Four changes from the operator's mockup, each with its reason in the generator:
    1. the active item follows the page (the mockups show Inditopult active on all)
    2. Teszteles is ALSO a primary button at the top of the lower group - it is the
       one action we want and the mockup buries it at the bottom
    3. the Alkalmazasok categories are anchors on /alkalmazasok: real URLs, no
       JS-only state
    4. ADDED GYIK. It is in today's nav; dropping it silently would take a page out
       of navigation, which is not a change a restyle gets to make.

scripts/site_gates.py - gate 3 extended rather than duplicated, as asked: a SHELL
  set whose pages must carry an IDENTICAL <nav class="sidebar"> after the active
  marker is normalised. RED-PROOFED: a one-character change to one menu label on a
  second shell page convicts. It also prints "DIFFER" rather than a reassuring
  "identical" count when it fails - a false reassurance printed beside a conviction
  is the exact defect this repo files rows about.

documentation/design/design-system.md - new "Shell" section: what is shared (tokens
  + shell + atoms), what each side owns, how a change flows (controller first, the
  website's copy the same week), and that the cross-repo gate is deliberately NOT
  built yet.

scripts/site_gates.py

@@ -115,9 +115,16 @@ MOCKUPS = {os.path.join("preview", "m1", "index.html"),
            os.path.join("preview", "m1", "kapcsolat.html"),
            os.path.join("preview", "m2", "index.html")}
 
-PAGES = list(TWINS) + list(TWINS.values()) + sorted(NO_TWIN) + sorted(MOCKUPS)
+# SHELL (2026-10-11, M3) — pages that wear the controller's frame instead of the website's
+# <nav>/<footer>. They are staged under /preview/m3/ until the operator's go, and at the switch
+# every live page becomes one of these. They keep every other check; what changes for them is
+# WHICH block has to be identical across the set: the sidebar, not the nav and footer. Gate 3
+# below does both, so there is one identity gate rather than two.
+SHELL = {os.path.join("preview", "m3", "index.html")}
+
+PAGES = list(TWINS) + list(TWINS.values()) + sorted(NO_TWIN) + sorted(MOCKUPS) + sorted(SHELL)
 EN_PAGES = set(TWINS.values())
-HU_PAGES = set(PAGES) - EN_PAGES - MOCKUPS
+HU_PAGES = set(PAGES) - EN_PAGES - MOCKUPS - SHELL
 ANALYTICS_EXEMPT = {"szolgaltatasok-nonpublic.html"} | MOCKUPS
 ANALYTICS_MARK = "https://stats.felhom.eu/script.js"
 SITE = "https://felhom.eu"
@@ -225,6 +232,37 @@ for lang, members, ref in (("hu", HU_PAGES, "index.html"), ("en", EN_PAGES, os.p
             fail("%s: <nav> differs from %s (after active-marker normalization)" % (p, ref))
         if foot != rfoot:
             fail("%s: <footer> differs from %s" % (p, ref))
+# gate 3b (2026-10-11, M3): the SHELL set carries a sidebar instead of the nav+footer, and that
+# sidebar is duplicated into every page because the site is static with no build step. The thing
+# that keeps the duplication honest is this check: every shell page's <nav class="sidebar"> block
+# must be identical once the active marker and the globe's current item are normalised away —
+# exactly the normalisation norm_block already does for the old chrome.
+_shell_by_lang = {}
+for p in sorted(SHELL):
+    s = pages.get(p)
+    if s is None:
+        continue
+    m = re.search(r'<nav class="sidebar" id="sidebar">.*?</nav>', s, re.DOTALL)
+    if not m:
+        fail("%s: no <nav class=\"sidebar\"> block — a shell page carries the shell" % p)
+        continue
+    _shell_by_lang.setdefault("en" if p.startswith("en" + os.sep) else "hu", []).append((p, norm_block(m.group(0))))
+for _lang, _members in sorted(_shell_by_lang.items()):
+    _ref_p, _ref = _members[0]
+    _bad = 0
+    for _p, _blk in _members[1:]:
+        if _blk != _ref:
+            _bad += 1
+            fail("%s: <nav class=\"sidebar\"> differs from %s (after active-marker normalization) — "
+                 "the shell is duplicated into every page, so it must be identical" % (_p, _ref_p))
+    # say "identical" ONLY when they are. A reassuring count printed next to a conviction is the
+    # same defect this repo files rows about.
+    if _bad:
+        print("  shell sidebar: %d of %d %s page(s) DIFFER from %s"
+              % (_bad, len(_members) - 1, _lang, _ref_p))
+    else:
+        print("  shell sidebar: %d %s page(s), all identical to %s" % (len(_members), _lang, _ref_p))
+
 if os.path.join("en", "index.html") in pages:
     _f = re.search(r"<footer>.*?</footer>", pages[os.path.join("en", "index.html")], re.DOTALL)
     if not _f or "households in Hungary" not in _f.group(0):