v0.4.0 — review findings become rules

Review findings become rules. Each finding from the v0.3.0 blind tests is fixed in its example and turned into a check, a probe rule, or a template line that applies to every explanation.

• Terms: terms in model.yaml lists the phrases a rendering must not use for a concept. explainer check fails on one. Probe rule 3 now asks for one name per concept.
• Meaning of quantities: probe rule 6 asks what each number shown means for the reader. check -v lists each accept_unjustified function as a debt.
• Pace: render and review report a claim with less than 1 s of pause after its line, or more than 10 s of narration over one picture after its mark.
• Blind-test audit: the reviewer also lists concepts with two names, numbers without a meaning, steps without a why, and (video) rushed points. The rubric treats each as a gap.
• Pages keep predict pauses: explainer check fails a page that plays a video with predict pauses through a plain <video>. The landing page now uses Explainer.video.
• Mermaid: explainer check --diagrams renders every Mermaid block with the pinned Mermaid CLI (mmdc or npx). CI runs it.
• Examples: dijkstra uses "estimate" for the tentative value and "distance" only for the final one; the finality argument is three lines, one step per picture, with pauses; relax is shown as a test. softmax-temperature replaces the entropy definition with a why-entropy claim (surprise in bits, why a log and not a count, live per-token surprise on the page), and pauses after why exp.
• Second-round fixes from the audit: softmax "scaled gap" (a terms entry, which also caught the page); Dijkstra's finality argument now draws the settled region as A and C, exits through D and E, and says why reaching D costs at least its estimate; the narration says each relaxation's sum. Probe rule 2 checks each step of an argument as written. Review-sheet headings show event times.
• Principles: §10 adds one name per concept, a meaning for each quantity, time for each claim, and "turn each review finding into a rule".

Full history: CHANGELOG.md