Citation Grounding Hatch

1"use client";
2 
3import { useEffect, useMemo, useRef, useState } from "react";
4 
5// BedrockTrace — a grounding instrument strip for a RAG answer. Citation
6// pills answer "what backs this claim"; this answers "how much of the WHOLE
7// answer is actually supported", including the dangerous unsupported middle
8// citation pills silently skip. One 3px core-sample track runs under the
9// prose, cut into one segment per sentence: a thick solid bar where a source
10// grounds the claim, a bare hairline where the model is inferring on its own
11// (the gap is drawn, not omitted), and a diagonal hatch where a source
12// actively contradicts the claim. Grounded/contradicted/unsupported is
13// shape-and-pattern encoded — solid / absent / hatched — never color, so it
14// survives grayscale and color-blindness. A static text legend ("Grounded /
15// Unsupported / Contradicted", each next to its own always-rendered swatch)
16// sits above the track so the encoding reads at rest, before anyone hovers,
17// focuses, or clicks a segment — the marks alone were review feedback
18// (twice) as illegible without that key.
19//
20// Every segment is a real <button>, labeled "Sentence N: supported by
21// Source B" / "no source" / "contradicted by Source C". Hovering OR
22// focusing a segment brightens its sentence in the prose above (and vice
23// versa) via a shared `data-sentence-id`, so keyboard users get the same
24// linkage sighted mouse users do. Clicking a grounded or contradicted
25// segment raises a glass detail panel with that source's excerpt, the
26// matching span underlined in accent — and the same accent underline lands
27// on the sentence itself, so the claim and its evidence light up together.
28// The panel expands via a CSS grid-template-rows 0fr->1fr trick (no
29// JS height measurement, no clipping-by-ancestor hazard).
30//
31// Segments reveal left-to-right via SVG stroke-dashoffset (pathLength=1, so
32// no pixel-length measurement is needed) starting ~300ms after a sentence
33// first appears in the `sentences` array — the trace visibly catches up to
34// prose that is still streaming in. A summary line ("4 of 6 sentences
35// grounded, 1 contradiction") is aria-live=polite and IS the sighted
36// digest, not a hidden echo of it. Zero dependencies; no canvas; every
37// color is a token (--background --foreground --muted --border --accent),
38// --accent appearing only on focus rings and the two interactive
39// highlights above. prefers-reduced-motion drops all transitions — the
40// … truncated