test_frontier_compare_report_viewer_exists was failing on main against
the current report_viewer.html because two verbatim substring checks
no longer matched the viewer's UI copy:
- "Drop report JSON" → viewer now says "Drop JSON report" (order swapped)
- "No network calls" → viewer now says "no network calls" (lowercase)
Both copy refreshes were behavior-preserving — drop-zone affordance
and network-free trust boundary are both intact in the viewer. The
test was coupling to verbatim phrasing rather than to the load-bearing
affordances.
Switch to case-insensitive substring checks that pin what actually
matters:
- "frontier compare" — viewer identity
- "drop" AND "json" together — drop-zone affordance, order-independent
- "no network calls" — trust boundary (case-insensitive)
- fetch(/XMLHttpRequest still hard-banned (case-sensitive — these
are JS API surface, not human-readable copy)
Pre-existing failure flagged in PR #66's body as out-of-scope cleanup;
this is that cleanup.
