fix(agent): Add refresh token validation before token refresh

Check for refresh token availability before attempting credential refresh.
Setup tokens that expire without a refresh token now return a clear error
instead of attempting an invalid refresh operation.

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

src/agent/process-manager.ts

@@ -68,6 +68,13 @@ export class ProcessManager {
       baseBranch
     }, 'creating project worktrees');
 
+    // No linked projects — fall back to standalone worktree so the agent
+    // always has a git-backed working directory.
+    if (projects.length === 0) {
+      log.info({ alias, initiativeId }, 'initiative has no linked projects, falling back to standalone worktree');
+      return this.createStandaloneWorktree(alias);
+    }
+
     for (const project of projects) {
       const clonePath = await ensureProjectClone(project, this.workspaceRoot);
       const worktreeManager = new SimpleGitWorktreeManager(clonePath, undefined, agentWorkdir);