feat(context): inject CLAUDE.md / AGENTS.md as L0 standing context

On session start, discover CLAUDE.md and AGENTS.md at the bound workspace root and inject
their (concatenated, header-labeled) contents as an L0 system context entry for every stage —
mirroring the .correx/project.toml ProjectProfile path end to end. Recorded as
AgentInstructionsBoundEvent (invariant #9) so replay reads the recorded fact, not the live
file; folded into SessionState.boundAgentInstructions and rendered by buildAgentInstructionsEntry
right after the project profile. AgentInstructionsLoader reads root-only, both files if present.
Bound via ServerModule.bindAgentInstructions alongside bindProjectProfile.

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

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

@@ -37,3 +37,12 @@ data class ProjectProfileBoundEvent(
     val conventions: List<String>,
     val commands: Map<String, String>,
 ) : EventPayload
+
+@Serializable
+@SerialName("AgentInstructionsBound")
+data class AgentInstructionsBoundEvent(
+    val sessionId: SessionId,
+    val workspaceRoot: String,
+    val sources: List<String>, // file names found, e.g. ["CLAUDE.md","AGENTS.md"]
+    val content: String,       // concatenated, header-labeled instructions
+) : EventPayload

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

@@ -1,5 +1,6 @@
 package com.correx.core.events.serialization
 
+import com.correx.core.events.events.AgentInstructionsBoundEvent
 import com.correx.core.events.events.ApprovalDecisionResolvedEvent
 import com.correx.core.events.events.ApprovalGrantCreatedEvent
 import com.correx.core.events.events.ApprovalGrantExpiredEvent
@@ -126,6 +127,7 @@ val eventModule = SerializersModule {
         subclass(SessionWorkspaceBoundEvent::class)
         subclass(OperatorProfileBoundEvent::class)
         subclass(ProjectProfileBoundEvent::class)
+        subclass(AgentInstructionsBoundEvent::class)
         subclass(L3MemoryRetrievedEvent::class)
         subclass(ContextTruncatedEvent::class)
         subclass(ExecutionPlanLockedEvent::class)

core/events/src/test/kotlin/com/correx/core/events/serialization/ProjectProfileBoundEventSerializationTest.kt

@@ -1,5 +1,6 @@
 package com.correx.core.events.serialization
 
+import com.correx.core.events.events.AgentInstructionsBoundEvent
 import com.correx.core.events.events.EventPayload
 import com.correx.core.events.events.ProjectProfileBoundEvent
 import com.correx.core.events.types.SessionId
@@ -24,6 +25,20 @@ class ProjectProfileBoundEventSerializationTest {
         assertEquals(sample, decoded)
     }
 
+    @Test
+    fun `AgentInstructionsBoundEvent round-trips as polymorphic EventPayload`() {
+        val sample: EventPayload = AgentInstructionsBoundEvent(
+            sessionId = SessionId("s1"),
+            workspaceRoot = "/repo",
+            sources = listOf("CLAUDE.md", "AGENTS.md"),
+            content = "# CLAUDE.md\n\nbe careful\n\n# AGENTS.md\n\nuse tools",
+        )
+        val encoded = eventJson.encodeToString(EventPayload.serializer(), sample)
+        assertTrue(encoded.contains("\"type\":\"AgentInstructionsBound\""), "SerialName must be present: $encoded")
+        val decoded = eventJson.decodeFromString(EventPayload.serializer(), encoded)
+        assertEquals(sample, decoded)
+    }
+
     @Test
     fun `round-trips with empty fields`() {
         val sample: EventPayload = ProjectProfileBoundEvent(