feat(router): idea-board -> project-profile promotion (E)

Promote an auto-captured idea from the cross-session board into the curated per-repo
profile at <workspaceRoot>/.correx/project.toml as a `conventions` entry. New
IdeaPromotedEvent tombstones the idea off the board (IdeaReader treats it like a
discard) and records the promotion as a fact; the server PromoteIdea handler loads
the profile, appends the idea text (deduped via ProjectProfile.withConvention), and
writes it back. Adds ProjectProfileWriter (escape-aware TOML serialize/write) and
makes SimpleToml's reader unescape \\ and \" symmetrically with the writers
(fixes a pre-existing read/write asymmetry surfaced by the round-trip test).

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

core/events/src/main/kotlin/com/correx/core/events/events/IdeaEvents.kt

@@ -31,3 +31,19 @@ data class IdeaDiscardedEvent(
     val ideaId: String,
     val sessionId: SessionId,
 ) : EventPayload
+
+/**
+ * The operator promoted an idea from the cross-session board into the curated per-repo profile
+ * (`<workspaceRoot>/.correx/project.toml`, as a `conventions` entry). Like [IdeaDiscardedEvent] this
+ * is a tombstone — the original [IdeaCapturedEvent] stays in the log (and replays), but the idea-board
+ * projection filters out any promoted [ideaId]. [sessionId] is the capturing session (so all of one
+ * idea's events stay co-located); [text] records the convention text written to the profile.
+ */
+@Serializable
+@SerialName("IdeaPromoted")
+data class IdeaPromotedEvent(
+    val ideaId: String,
+    val sessionId: SessionId,
+    val text: String,
+    val timestampMs: Long,
+) : EventPayload

core/events/src/main/kotlin/com/correx/core/events/serialization/Serialization.kt

@@ -29,6 +29,7 @@ import com.correx.core.events.events.HealthDegradedEvent
 import com.correx.core.events.events.HealthRestoredEvent
 import com.correx.core.events.events.IdeaCapturedEvent
 import com.correx.core.events.events.IdeaDiscardedEvent
+import com.correx.core.events.events.IdeaPromotedEvent
 import com.correx.core.events.events.JournalCompactedEvent
 import com.correx.core.events.events.FileWrittenEvent
 import com.correx.core.events.events.L3MemoryRetrievedEvent
@@ -137,6 +138,7 @@ val eventModule = SerializersModule {
         subclass(WorkflowProposedEvent::class)
         subclass(IdeaCapturedEvent::class)
         subclass(IdeaDiscardedEvent::class)
+        subclass(IdeaPromotedEvent::class)
         subclass(CritiqueOutcomeCorrelatedEvent::class)
         subclass(StageCheckpointPassedEvent::class)
         subclass(StageCheckpointFailedEvent::class)

core/events/src/test/kotlin/com/correx/core/events/EventSerializationHardeningTest.kt

@@ -6,6 +6,7 @@ import com.correx.core.approvals.Tier
 import com.correx.core.events.events.ApprovalDecisionResolvedEvent
 import com.correx.core.events.events.ApprovalRequestedEvent
 import com.correx.core.events.events.EventPayload
+import com.correx.core.events.events.IdeaPromotedEvent
 import com.correx.core.events.events.OrchestrationPausedEvent
 import com.correx.core.events.events.RiskAssessedEvent
 import com.correx.core.events.events.SteeringNoteAddedEvent
@@ -81,6 +82,12 @@ class EventSerializationHardeningTest {
             terminalStageId = stageId,
             totalStages = 1,
         ),
+        "IdeaPromoted" to IdeaPromotedEvent(
+            ideaId = "idea-1",
+            sessionId = sessionId,
+            text = "cache the repo map across sessions",
+            timestampMs = 1_700_000_000_000,
+        ),
     )
 
     @Test