fix(ui): give the mobile refresh controls labels and full width

At <=640px the RAG "Sync sources" pill and the History "Refresh"
pill squeezed down to tiny icon-only buttons — hard to discover and
tap on a phone. They are now full-width labeled pills:

- the RAG page-head row wraps so the Sync pill drops below the
  "Knowledge base" title at full width; the History page-head
  already wrapped the pill below its title block
- the Sync label's min(16rem, 40vw) cap lifts on mobile (min-width: 0
  engages the ellipsis) so the live-file text truncates against the
  full width instead of the 40vw cap
- the Refresh glyph joins its visible label (it stays hidden on
  desktop, where the label carries the pill)

This matches the established mobile full-width pill language (New
chat / Share / stale-ban Regenerate). The three unit tests that
pinned the old icon-only CSS are updated to pin the new behavior.

tests/unit/test_frontend_router.py

@@ -721,9 +721,9 @@ def test_history_refresh_button_css_reuses_the_new_chat_language() -> None:
     hidden on desktop (the label carries the pill) — and the global
     :focus-visible ring applies (no button-scoped focus override).
     The page-head flex row is SCOPED to #view-history (the other four
-    views' page-heads are untouched). Below 640px the pill goes
-    icon-only (the phase-46 auth-link convention — the aria-label
-    keeps the accessible name)."""
+    views' page-heads are untouched). Below 640px the pill goes full
+    width with the label visible (the icon-only squeeze is gone —
+    the glyph joins the label)."""
     css = _asset("styles.css")
     block = re.search(r"\.history-refresh \{([\s\S]*?)\n\}", css)
     assert block, "styles.css must style .history-refresh"
@@ -746,11 +746,11 @@ def test_history_refresh_button_css_reuses_the_new_chat_language() -> None:
     mobile = re.search(r"@media \(max-width: 640px\) \{([\s\S]*?)\n\}\n", css)
     assert mobile, "the 640px media query must exist"
     mbody = mobile.group(1)
-    assert ".history-refresh-label { display: none; }" in mbody, (
-        "icon-only below 640px (the phase-46 convention)"
+    assert ".history-refresh { width: 100%; }" in mbody, (
+        "full width below 640px (the icon-only squeeze is gone)"
     )
     assert ".history-refresh svg { display: block; }" in mbody, (
-        "the glyph is the whole control below 640px"
+        "the glyph joins the visible label below 640px"
     )