A genuinely-clear or uncrackable extra title (a tiny menu/nav stub) no
longer poisons a multi-title rip with a false CssKeyMissing (E7023).
- decrypt_keys_for_title_checked: re-crack a non-overlapping VTS via
crack_key_outcome and report title_is_clear when the title's own
extents show no scrambling. A genuinely-clear stub on an otherwise-CSS
disc needs no key.
- ensure_title_decryptable: pass a clear stub without a key; a scrambled-
but-uncrackable title still hard-fails with CssKeyMissing.
- is_scrambled_pack: hardened scramble-evidence gate for the crack scan —
requires the MPEG-PS pack-start signature before trusting the 0x14
scramble bits, so a clear stub with stray 0x14 bits can't flip
saw_scrambled. The descramble loop keeps the looser is_scrambled.
- mux/resolve: ISO per-title gate routes through the clear-aware check.