fix(background-agent): pass query directory to session.get in 4 call-sites (#2937)

resolveSubagentSpawnContext and related lookups called client.session.get
without the query.directory parameter, causing project-scoped sessions
to 404 under newer OpenCode SDK versions. Threaded directory through
SpawnerContext/BackgroundManager so all four call-sites pass it.

🤖 Generated with OhMyOpenCode assistance
https://github.com/code-yeongyu/oh-my-opencode

src/features/background-agent/subagent-spawn-limits.ts

@@ -20,7 +20,8 @@ export function getMaxRootSessionSpawnBudget(config?: BackgroundTaskConfig): num
 
 export async function resolveSubagentSpawnContext(
   client: OpencodeClient,
-  parentSessionID: string
+  parentSessionID: string,
+  directory?: string
 ): Promise<SubagentSpawnContext> {
   const visitedSessionIDs = new Set<string>()
   let rootSessionID = parentSessionID
@@ -38,6 +39,7 @@ export async function resolveSubagentSpawnContext(
     try {
       const response = await client.session.get({
         path: { id: currentSessionID },
+        ...(directory ? { query: { directory } } : {}),
       })
       if (response.error) {
         throw new Error(String(response.error))