quiz answers carry a confidence slider — raw probability, snapped 0/30/50/70/90/100

Owner design round 2026-10-01: every multiple-choice quiz answer now
carries the learner's stated probability that his selected answer is
correct — calibration data for the prober and teacher, the flow itself
unchanged.

Definition (owner ruling, after weighing chance-normalization): RAW
probability. Sub-chance reports are diagnostic gold, not dead space —
'picked an option, believes it wrong' is a real state. The agents get
the sophistication: new shared/25-confidence.md composes for both
agents (chance level, sub-chance = distrusts the pick, correct+low =
fragile, wrong+high = committed misconception, IDK = genuine gap).

- question-core: AnswerRequest/QuestionAnswerData.confidence (quiz
  only, optional — old records valid), buildAnswer clamps and drops it
  on dontKnow, formatAnswerMessage states the line, CONFIDENCE_STOPS +
  DEFAULT_CONFIDENCE_INDEX exported.
- question-dock: snapped slider below 'I don't know', above 'Your
  thinking' — native range over the stop INDEX so ←/→ step the uneven
  grid cleanly, Tab chain rows → slider → thinking, Enter submits from
  the slider too. Rests at 50 and always sends (owner: 50 must mean a
  real coin flip, never 'untouched'). 'I don't know' GRAYS it out —
  layout holds, no value sent.

Deliberately untouched: explain free-recall card (quiz-only scope),
answered-card rendering of confidence, ask flow.

src/agent/prompts/shared/25-confidence.md

@@ -0,0 +1,11 @@
+## Confidence — reading the learner's self-assessment
+
+Every quiz answer arrives with a `Confidence: N%` line: the learner's stated probability that his selected answer is correct, set on a snapped slider (0, 30, 50, 70, 90, 100). This is calibration data, not decoration. Read it against the verdict:
+
+- 50 is a genuine coin flip. 90–100 claims certainty; 0–30 claims real doubt.
+- For an n-option question, chance is 1/n. Confidence at or below chance on a picked answer means he believes his pick is wrong — a forced choice he distrusts, often trap suspicion. Treat it as honesty, not error.
+- Correct + high confidence: solid knowledge — move on.
+- Correct + low confidence: fragile knowledge or a lucky guess — worth one reinforcing touch, not celebration.
+- Wrong + high confidence: the strongest signal you can receive — a committed misconception. Name the crack, probe it gently, and re-teach around it.
+- Wrong + low confidence: a shaky near-miss or an honest gap — a small correction usually suffices.
+- "I don't know" carries no confidence line: he declined to guess. A genuine gap, never a wrong answer.