Add v2_a11 describability axis (one-sentence buyer-language test)

Append an 11th filter `describability` to the FILTERS array in filter_score.js. Question: 'Can this product be described to the named buyer in ONE sentence using that buyer's own vocabulary, with no AE-internal jargon (graded/scorecard/calibration/audit/preflight)?' Both reviewers score 0-3 alongside existing 5 filters. 3 = buyer-vocabulary one-liner present in description; 2 = present but loaded with one AE-internal token; 1 = requires explaining AE's mechanism to make sense; 0 = title or first sentence is mechanism-as-product ('Pre-send claim gate for...'). Composite formula unchanged in shape — divisor moves from 15 to 18, kill rules untouched. Two-consecutive-zero categorical kill extends to the new axis automatically.

Hypotheses whose title leads with AE's mechanism (e.g. forecast-audit / claim-gate / drift-ledger pattern — the 847f7e shape) score 0-1 on v2_a11; hypotheses whose title leads with the buyer's pain ('Dental practice software complaints triage') score 2-3. Predicted 1.5-2.5 point composite spread between the two shapes on a replay of the last 30 admitted hypotheses.

Run scoring on the 30 most recent admitted hypotheses (any phase). If v2_a11 score does not correlate (Spearman |rho| < 0.3) with whether the title contains an AE-jargon token from the closed-list {graded, scorecard, gate, preflight, ledger, audit, drift}, the axis is measuring something other than describability and should be removed.

Passed the council verdict. Awaiting Commander decision — approve, reject, or defer.