docs: document synthesize — the verdict priority is the honesty policy

[bhyi4]

Found by a consistency audit across all five mirror repos.

synthesize was in __all__ — a public API promise — with zero mentions in README, README_KO or either GUIDE. It is not a minor helper: its check order is the honesty policy, so the one function encoding the policy was the one you had to read source to find.

What was added

The five-row priority table, in both languages, with the reason each rank sits where it does:

Priority	Verdict	Why this order
1	TAMPERED	A broken integrity signal outranks everything — if the bytes were altered, nothing read from them can be trusted
2	CONFLICTING	Disagreement is reported as disagreement; silently picking a winner manufactures a certainty the evidence does not support
3	SYNTHETIC	An AI-origin assertion is positive evidence
4	AUTHENTIC-SIGNED	A signature is present. ⚠️ PoC: the crypto chain is not yet verified
5	UNVERIFIED	The honest default — no signal means unknown, not evidence of fakery

Row 5 is the point of the package. Absence of a provenance signal is overwhelmingly common in authentic media too — most real photos carry no C2PA manifest — so a tool that answers "fake" when it cannot tell is worse than no tool.

Guard

tests/test_synthesize_priority.py pins all five rows against the code and asserts both README tables list them in that order, so the documented policy cannot drift from the implemented one. All five rows were verified against the running code before being written down.

49 tests pass (was 41). Docs only — no behaviour change.

🤖 Generated with Claude Code