fix: make sessionExists() async with SDK verification on SQLite

sessionExists() previously returned unconditional true on SQLite,
preventing ralph-loop orphaned-session cleanup from triggering.
Now uses sdkClient.session.messages() to verify session actually
exists. Callers updated to await the async result.

Addresses Cubic review feedback on PR #1837.

src/plugin/hooks/create-session-hooks.ts

@@ -122,7 +122,7 @@ export function createSessionHooks(args: {
     ? safeHook("ralph-loop", () =>
         createRalphLoopHook(ctx, {
           config: pluginConfig.ralph_loop,
-          checkSessionExists: async (sessionId) => sessionExists(sessionId),
+          checkSessionExists: async (sessionId) => await sessionExists(sessionId),
         }))
     : null
 

src/tools/session-manager/storage.test.ts

@@ -78,15 +78,15 @@ describe("session-manager storage", () => {
     expect(result).toBe(sessionPath)
   })
 
-  test("sessionExists returns false for non-existent session", () => {
+  test("sessionExists returns false for non-existent session", async () => {
     // when
-    const exists = sessionExists("ses_nonexistent")
+    const exists = await sessionExists("ses_nonexistent")
 
     // then
     expect(exists).toBe(false)
   })
 
-  test("sessionExists returns true for existing session", () => {
+  test("sessionExists returns true for existing session", async () => {
     // given
     const sessionID = "ses_exists"
     const sessionPath = join(TEST_MESSAGE_STORAGE, sessionID)
@@ -94,7 +94,7 @@ describe("session-manager storage", () => {
     writeFileSync(join(sessionPath, "msg_001.json"), JSON.stringify({ id: "msg_001" }))
 
     // when
-    const exists = sessionExists(sessionID)
+    const exists = await sessionExists(sessionID)
 
     // then
     expect(exists).toBe(true)

src/tools/session-manager/storage.ts

@@ -138,8 +138,16 @@ export function getMessageDir(sessionID: string): string | null {
   return null
 }
 
-export function sessionExists(sessionID: string): boolean {
-  if (isSqliteBackend()) return true
+export async function sessionExists(sessionID: string): Promise<boolean> {
+  if (isSqliteBackend() && sdkClient) {
+    try {
+      const response = await sdkClient.session.messages({ path: { id: sessionID } })
+      const messages = response.data as unknown[] | undefined
+      return Array.isArray(messages) && messages.length > 0
+    } catch {
+      return false
+    }
+  }
   return getMessageDir(sessionID) !== null
 }
 

src/tools/session-manager/tools.ts

@@ -70,7 +70,7 @@ export function createSessionManagerTools(ctx: PluginInput): Record<string, Tool
     },
     execute: async (args: SessionReadArgs, _context) => {
       try {
-        if (!sessionExists(args.session_id)) {
+        if (!(await sessionExists(args.session_id))) {
           return `Session not found: ${args.session_id}`
         }