Add audit and session log record types to proto

Implemented-By: Laguna S 2.1 (OpenCode)

crates/proto/src/log.rs

@@ -0,0 +1,54 @@
+//! Session log record types. One JSON object per line; assistant messages are stored verbatim.
+
+use serde::{Deserialize, Serialize};
+
+use crate::{CallId, DataClass, Epoch, Hash32, SessionId, Timestamp};
+
+#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
+pub struct ToolCall {
+    pub id: String,
+    pub name: String,
+    pub arguments: String,
+}
+
+// JSON: {"type":"user","time":"…","content":"…"} ; the tag sits beside the fields; types are snake_case
+#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
+#[serde(tag = "type", rename_all = "snake_case", deny_unknown_fields)]
+pub enum LogRecord {
+    SessionStart {
+        time: Timestamp,
+        session: SessionId,
+        epoch: Epoch,
+        slot: u32,
+        baseline: Hash32,
+    },
+    User {
+        time: Timestamp,
+        content: String,
+    },
+    Assistant {
+        time: Timestamp,
+        content: Option<String>,
+        reasoning_content: Option<String>,
+        tool_calls: Vec<ToolCall>,
+    },
+    ToolResult {
+        time: Timestamp,
+        call: CallId,
+        tool_call_id: String,
+        content: String,
+        class: DataClass,
+        untrusted: bool,
+        truncated: bool,
+    },
+    CacheLoss {
+        time: Timestamp,
+        expected: u64,
+        got: u64,
+    },
+    EpochEnd {
+        time: Timestamp,
+        next: Epoch,
+        summary: String,
+    },
+}