chandra and olmOCR each set `meta.confidence` and `meta.confidence_measured`.
surya set neither: its predictor reports confidence per LINE, so a caller
switching engines was handed a different kind of answer, and nothing could tell
"no line reported a confidence" from "the model was certain it was unsure".

Now it reports both. Weighted by CHARACTERS rather than per line, because the
other two average over tokens -- that is, over text -- and a plain line-mean
lets a two-word line count as much as a full one: on
[(100 chars, 0.95), (2 chars, 0.1)] it answers 0.9333 instead of 0.525.

`confidence_measured` is the half that earns its place, and the reason the
aggregate reads the RAW value rather than the per-line field: that field has to
coerce a missing confidence to 0.0 for its own sake, which would make

    nothing reported  -> 0.0
    a real zero       -> 0.0

indistinguishable. One such 0.0 has already produced a confidently wrong
verdict in this subsystem. So:

    nothing reported  -> (0.0, False)
    a real zero       -> (0.0, True)
    mixed             -> unreported lines skipped, never counted as zero

Both keys reach the caller with no new plumbing: `_page_from_dict` forwards
unknown keys by EXCLUSION (a choice made after that reassembly silently dropped
`accents_repaired`, and then `model_attempts`), and both are already in the
pod->orchestrator whitelist, so a page read on a rented pod reports what a
local one does. Tested, including that `False` is not mistaken for the empty
value that exclusion filter skips.

The aggregate is extracted as `_page_confidence()` so it is testable without
surya installed.

Worth recording what this is NOT: on the page where the accent bug was found,
surya reported ~96 % per line while every accent was a replacement character --
confident, and right to be, having emitted the correct tokens. Confidence is
not a corruption detector; the byte trace is.

13 new tests. 3447 passed, 13 pre-existing failures (broker, studio, manual
client) untouched.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01KnfkxBpcZ1v6ypRFFyhrVM