FU-05 core (closes#11652): caller-supplied Video Bridge transcripts had no bounded, deterministic contract — a client could self-assert source: "embedded"/"audio-bridge" and it was accepted verbatim. normalizeVideoTranscript gained a code-only trustedSource seam unreachable from request-body JSON; without it, any cue declaring embedded/audio-bridge is reclassified to client. Added budgets (256 cues, 4096 code units/cue, 4KiB/cue, 64KiB total), malformed-surrogate rejection, focus-window scoping, deterministic cross-source reconciliation, and bumped the result-cache version v4→v5 so old-contract cache entries can never serve new-contract requests.
All 187 videoBridge* tests pass (185 pass, 2 unrelated pre-existing skips).
