fix: recognize Cursor session-not-found error format

[log-li]

Summary

Cursor CLI returns error code -32602 with message Session "xxx" not found when session/load fails. This format was not recognized by isSessionNotFoundText(), preventing fallback to session/new.

Problem

When OpenClaw tries to spawn a Cursor ACP session using sessions_spawn(runtime="acp", agentId="cursor"), the following error occurs:

Invalid params - Session "xxx" not found

The root cause is that Cursor's error message format Session "xxx" not found contains the session ID in the middle, so "session not found" is not a substring.

Solution

Added regex pattern to match Session "xxx" not found format:

const SESSION_NOT_FOUND_PATTERN = /session\s+["'\w\-]+\s+not found/i;

Testing

• ✅ Unit tests pass (254 tests, 0 failures)
• ✅ Verified with real Cursor CLI error format
• ✅ End-to-end test with OpenClaw sessions_spawn successful

Fixes #161