feat: freeze Host Journal context across compaction

crates/session-store/src/history.rs

@@ -69,6 +69,8 @@ pub enum LoggedSessionHistoryOrigin {
     },
     /// Host-produced opening context summary; not auto-read or TaskStore material.
     CompactionSummary,
+    /// Frozen Host Journal reference, never independent observation evidence.
+    JournalContext,
     DerivedSummary,
     LegacyUnknown,
 }

crates/session-store/src/public_material.rs

@@ -829,7 +829,9 @@ fn boundary_reference(
 fn canonical_body(entry: &LoggedHistoryEntry) -> Option<CanonicalBody<'_>> {
     if matches!(
         entry.metadata.origin,
-        LoggedSessionHistoryOrigin::DerivedSummary | LoggedSessionHistoryOrigin::CompactionSummary
+        LoggedSessionHistoryOrigin::DerivedSummary
+            | LoggedSessionHistoryOrigin::CompactionSummary
+            | LoggedSessionHistoryOrigin::JournalContext
     ) {
         return None;
     }

crates/session-store/src/public_material/tests.rs

@@ -543,6 +543,14 @@ fn reasoning_proves_rollback_safety_but_private_and_derived_items_are_not_materi
     let segment = crate::new_segment_id();
     let mut derived = message("derived", LoggedRole::User, "summary");
     derived.metadata.origin = LoggedSessionHistoryOrigin::DerivedSummary;
+    let mut journal = message("journal", LoggedRole::User, "frozen Journal reference");
+    journal.metadata.origin = LoggedSessionHistoryOrigin::JournalContext;
+    let mut summary = message(
+        "compaction-summary",
+        LoggedRole::User,
+        "complementary summary",
+    );
+    summary.metadata.origin = LoggedSessionHistoryOrigin::CompactionSummary;
     let reasoning = entry(
         "reasoning",
         LoggedItem::Reasoning {
@@ -559,7 +567,12 @@ fn reasoning_proves_rollback_safety_but_private_and_derived_items_are_not_materi
             &[
                 seed(
                     session,
-                    vec![derived, message("system", LoggedRole::System, "secret")],
+                    vec![
+                        derived,
+                        journal,
+                        summary,
+                        message("system", LoggedRole::System, "secret"),
+                    ],
                 ),
                 LogEntry::AnnotatedSystemItem {
                     ts: 1,

crates/session-store/src/public_snapshot.rs

@@ -1889,6 +1889,7 @@ fn provenance(origin: &LoggedSessionHistoryOrigin) -> SessionEntryProvenance {
         LoggedSessionHistoryOrigin::ModelOutput { .. } => SessionEntryProvenance::ModelOutput,
         LoggedSessionHistoryOrigin::ToolOutput { .. } => SessionEntryProvenance::ToolOutput,
         LoggedSessionHistoryOrigin::CompactionSummary
+        | LoggedSessionHistoryOrigin::JournalContext
         | LoggedSessionHistoryOrigin::DerivedSummary => SessionEntryProvenance::DerivedSummary,
         LoggedSessionHistoryOrigin::LegacyUnknown => SessionEntryProvenance::LegacyUnknown,
     }