Adds two InferredParams (TTL=7d) computed from 28-day rolling daily done counts:
- baseline_completions_per_day: mean done events/day over the window
- stdev: stdev of daily counts (floored at 0.1 to avoid division by zero)
MomentumAgent.compute() now calculates a z-score from recent done events in
inp.feedback_history vs the inferred baseline. Snippet language switches to
z-score framing ("above your usual pace", "slowing down") when |z| >= 1.0,
falling back to engagement_trend labels when in the normal range.
- engagement_trend InferredParam preserved for backward compatibility
- momentum_window pref added (default 7, user-overridable)
- 14 new tests covering power user, casual user, returning-from-break, and
relative stdev comparison; engagement_trend tests updated for z-score priority
- Agent bumped to v1.2.0
Closes#114
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
alvis
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