feat(context): render retry repair mandate as final user turn (#293)

buildRetryFeedbackEntry was L1/SYSTEM, so PromptRenderer folded it into the
leading system block — far from the assistant/tool transcript and weaker than
the original stage task. Flip it to USER role and give the renderer an explicit
trailing repair-mandate slot (a sourceType set, extensible for recovery later):
repair mandates are lifted out of the inline flow and emitted once as the final
message, after the tool evidence and the steering anchor. retryFeedback is
already in REQUIRED_SOURCE_TYPES so it stays unprunable. Golden renderer test
proves the final message is the repair USER mandate and leading system no longer
carries it.

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

core/kernel/src/main/kotlin/com/correx/core/kernel/orchestration/ContextFeedback.kt

@@ -71,7 +71,9 @@ fun buildRetryFeedbackEntry(events: List<StoredEvent>, stageId: StageId): Contex
         sourceType = "retryFeedback",
         sourceId = stageId.value,
         tokenEstimate = content.length / 4,
-        role = EntryRole.SYSTEM,
+        // #293: USER (not SYSTEM) so PromptRenderer routes it to the trailing repair-mandate slot —
+        // the final message after the tool transcript — rather than folding it into leading system.
+        role = EntryRole.USER,
     )
 }