PASS: source guard rejects the original constructor/use expression and accepts the corrected source.
This is a pattern assertion, not Android API type checking.

PASS project invariants: XML, permission-free manifest, isolated PDF service, narrow FileProvider, portable core, no WebView/log calls.
PASS browser source invariants: APP_FILES/GET_CONTENT, standard picker activity, no system-picker impersonation, narrow copied paths, read-only results, sanitized activity defaults, debug fixture excluded from main manifest.
PASS PDF source regression guard: no PdfDocument().use call (pattern check only).