feat(context): purify leading SYSTEM, route context layers as USER turns (#290)

Move intent, repo map, docs catalog, decision journal and relevant-files
context entries to EntryRole.USER so they no longer fold into the single
leading SYSTEM block — that block stays pure policy/schema. Omit L3 repo-map
retrieval on repair retries (the transcript already carries the evidence).
Add "initialIntent" to REQUIRED_SOURCE_TYPES.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

testing/deterministic/src/test/kotlin/PromptRendererOrderingTest.kt

@@ -123,6 +123,29 @@ class PromptRendererOrderingTest {
         )
     }
 
+    @Test
+    fun `USER-role context entries render as separate turns and never fold into system`() {
+        // #290: intent, repo map, docs catalog and decision journal carry EntryRole.USER so the
+        // leading system block stays pure policy/schema. They must appear as user turns, not merge in.
+        val pack = ContextPack(
+            id = ContextPackId("p"),
+            sessionId = sessionId,
+            stageId = stageId,
+            layers = mapOf(
+                ContextLayer.L0 to listOf(entry("policy", ContextLayer.L0, EntryRole.SYSTEM, "systemPrompt")),
+                ContextLayer.L1 to listOf(entry("intent", ContextLayer.L1, EntryRole.USER, "initialIntent")),
+                ContextLayer.L3 to listOf(entry("journal", ContextLayer.L3, EntryRole.USER, "decisionJournal")),
+            ),
+            budgetUsed = 30,
+            budgetLimit = 4000,
+        )
+        val messages = PromptRenderer.render(pack)
+        assertEquals("policy", messages.first().content, "leading system must be policy only")
+        org.junit.jupiter.api.Assertions.assertEquals(1, messages.count { it.role == "system" })
+        org.junit.jupiter.api.Assertions.assertTrue(messages.any { it.role == "user" && it.content == "intent" })
+        org.junit.jupiter.api.Assertions.assertTrue(messages.any { it.role == "user" && it.content == "journal" })
+    }
+
     @Test
     fun `non-L0 SYSTEM entries fold into the single leading system message`() {
         // Strict chat templates (Qwen) 400 on any system message after index 0. Recalled L3