CPO: cluster layer semantic rename hop 2 — screen → percepts
Rename the screen source type to percepts across the cluster layer,
muse configs, CLI, importers, stats, and all tests. The entry prefix
changes from "screen" to "percept" (singular, matching "transcript").
The rendering header "### Screen Activity" is unchanged — it describes
the content origin, not the source type. Agent filter dicts like
{"agents": {"screen": true}} are also unchanged as they reference
agent output filenames.
Also updates inline muse configs in test_generate_full.py and
test_output_hooks.py from old "audio"/"screen" keys to
"transcripts"/"percepts" (audio was stale since hop 1).
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>