prompts: Voice + Accuracy become shared fragments — one law across every agent (round 13 part A)

- shared/10-voice.md (agent-neutral) + shared/15-accuracy.md (research-tool
  truth contract) compose for teacher, prober, AND practice
- PRACTICE_SHARED_FRAGMENTS grows beyond 40-formatting.md
- practice 00-base.md drops its stale near-copy ("You have no research tool
  here" was false since round 10); the solve-and-shortcut-hunt line folds
  into the problem paragraph
- teaching system-prompt.md slims (Voice/Accuracy sections removed)
- pins updated: practice-agents composition, prompt-overrides segment mirror

tests/practice-agents.test.ts

@@ -251,6 +251,20 @@ describe("practice prompt composition (own directory + the formatting appendix)"
 		assert.doesNotMatch(prompt, /predict/i);
 	});
 
+	it("the SHARED voice + accuracy compose (owner round 13): ONE law across every agent, and the stale line is dead", () => {
+		const prompt = composeInstructions("practice");
+		// accuracy: the shared chunk's research-tool reference (round 10 gave
+		// practice research — the old near-copy said "You have no research
+		// tool here", which was false)
+		assert.match(prompt, /one confidently-delivered hallucination poisons that/);
+		assert.match(prompt, /you have a `research` tool/);
+		assert.ok(!prompt.includes("no research tool here"), "the stale line is gone");
+		// the teacher composes the same shared chunks (one law)
+		const teacher = composeInstructions("teacher");
+		assert.match(teacher, /one confidently-delivered hallucination poisons that/);
+		assert.match(teacher, /Everything in this section deletes a default/);
+	});
+
 	it("the SHARED formatting guide composes (owner, 2026-10-04 late): LaTeX delimiters in every setting", () => {
 		const prompt = composeInstructions("practice");
 		// The delimiter law — practice must write \(...\)/\[...\] too.