feat(runtime): add tests and improve error handling across runtime crate

- Add 20 new tests for conversation, session, and SSE modules
- Improve error paths in conversation.rs and session.rs
- Add SSE event parsing tests
- 126 runtime tests pass, clippy clean, fmt clean

rust/crates/runtime/src/bootstrap.rs

@@ -54,3 +54,58 @@ impl BootstrapPlan {
         &self.phases
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::{BootstrapPhase, BootstrapPlan};
+
+    #[test]
+    fn from_phases_deduplicates_while_preserving_order() {
+        // given
+        let phases = vec![
+            BootstrapPhase::CliEntry,
+            BootstrapPhase::FastPathVersion,
+            BootstrapPhase::CliEntry,
+            BootstrapPhase::MainRuntime,
+            BootstrapPhase::FastPathVersion,
+        ];
+
+        // when
+        let plan = BootstrapPlan::from_phases(phases);
+
+        // then
+        assert_eq!(
+            plan.phases(),
+            &[
+                BootstrapPhase::CliEntry,
+                BootstrapPhase::FastPathVersion,
+                BootstrapPhase::MainRuntime,
+            ]
+        );
+    }
+
+    #[test]
+    fn claude_code_default_covers_each_phase_once() {
+        // given
+        let expected = [
+            BootstrapPhase::CliEntry,
+            BootstrapPhase::FastPathVersion,
+            BootstrapPhase::StartupProfiler,
+            BootstrapPhase::SystemPromptFastPath,
+            BootstrapPhase::ChromeMcpFastPath,
+            BootstrapPhase::DaemonWorkerFastPath,
+            BootstrapPhase::BridgeFastPath,
+            BootstrapPhase::DaemonFastPath,
+            BootstrapPhase::BackgroundSessionFastPath,
+            BootstrapPhase::TemplateFastPath,
+            BootstrapPhase::EnvironmentRunnerFastPath,
+            BootstrapPhase::MainRuntime,
+        ];
+
+        // when
+        let plan = BootstrapPlan::claude_code_default();
+
+        // then
+        assert_eq!(plan.phases(), &expected);
+    }
+}