I1: _DERIVER_TOKEN_COMBOS was factored task-independently, materializing the
impossible (ingestion, input, previous_summary) series — previous_summary is
summary-only. Make combos task-aware (_DERIVER_TOKEN_COMBOS_BY_TASK) so no
always-0 impossible series is fabricated, matching the PR's own goal. Tests
tightened to assert the ingestion/previous_summary series is absent.
I2: the three gauge .set(0) zero-inits were bare while the counter inits go
through the fail-soft _touch. Add _set_gauge_zero() so a gauge init can't
propagate an exception into process startup either.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
01cd20aa91