Report unclassified files from graphify update too

graphify extract has printed this since #1692, but the update and
watch rebuild path never did, so a corpus with no extractor for its
language, Lean 4 in the reported case, rebuilt successfully with
those files completely absent and nothing said about it. Prints the
same wording from the extract command, and threads the count into
the local detection summary the rebuild path already builds for
GRAPH_REPORT.md, which previously dropped it. Fixes #3511.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017qfdzgbA5KedGEjD1AayNh
(cherry picked from commit 120405673f7b35840158028d14bb54a71a89e763)