practice: the chain table — every reasoning chain in one selectable overlay (owner-approved plan, 2026-09-29)

- core formatChainLine: names + arrow one-liner, singleton marker, pure
- graph-view Chains button (chrome row, empty-graph hidden) opens the
  overlay: fuzzy search (names/aliases/statements), collapsible chain →
  member → statement rows, birth-session + created columns, no
  understanding-levels column
- pinned Selected section derives the agents' actual input live
  (chainsForSelection over the selection; premise without its
  conclusion shows as the singleton it becomes)
- Generate opens the creation dialog in CUSTOM mode: selection summary
  + dated default title, posts {nodeIds, params, note}; cluster mode
  untouched on /practice
- live-verified on the owner's dev server: 219 chains, derived preview,
  search-never-filters-Selected, dialog handoff (selection pass-through
  bug caught + fixed en route), Esc/backdrop dismiss, zero writes
- practice UI files re-normalized to tabs (my earlier prettier runs had
  drifted them to the 2-space default; whitespace-only)

17 render/unit pins added; gates: tsc 0, 1174/1174, lint 0, build 0

tests/practice.test.ts

@@ -9,7 +9,7 @@
 import assert from "node:assert/strict";
 import { describe, it } from "node:test";
 import type { EdgeType } from "../src/core/contracts.ts";
-import { chainCoverage, chainsForSelection, chainsToGraph } from "../src/core/practice.ts";
+import { chainCoverage, chainsForSelection, chainsToGraph, formatChainLine } from "../src/core/practice.ts";
 
 // ─── fixtures ────────────────────────────────────────────────────────────────
 
@@ -138,3 +138,24 @@ describe("chainCoverage", () => {
 		assert.deepEqual(chainCoverage(set), { missing: [], duplicated: [] });
 	});
 });
+
+describe("formatChainLine (the chain table's one-line shape, 2026-09-29)", () => {
+	const props = {
+		p1: { name: "Premise one" },
+		p2: { name: "Premise two" },
+		c1: { name: "Conclusion" },
+		solo: { name: "Standalone" },
+	};
+
+	it("joins sorted premise NAMES by the derivation arrow", () => {
+		assert.equal(formatChainLine({ premises: ["p2", "p1"], conclusion: "c1" }, props), "Premise one, Premise two → Conclusion");
+	});
+
+	it("a singleton shows its (no premises) marker", () => {
+		assert.equal(formatChainLine({ premises: [], conclusion: "solo" }, props), "Standalone (no premises)");
+	});
+
+	it("unknown ids fall back to the raw id (honest, never guessed)", () => {
+		assert.equal(formatChainLine({ premises: ["ghost"], conclusion: "c1" }, props), "ghost → Conclusion");
+	});
+});