[langgenius/dify] Fix issue #38539: agent prompt auto-generation uses invalid model_config.mode

Job description

Fix GitHub issue 38539 in langgenius/dify: https://github.com/langgenius/dify/issues/38539 Repo: https://github.com/langgenius/dify Target: Fix the Agent app prompt auto generation flow so /console/api/rule generate receives a valid model config.mode such as chat, not the app mode value agent chat. Required deliverables: A real frontend code change upstream against langgenius/dify. An upstream pull request linked to issue 38539. Testing notes covering the affected auto generation flow. The final OpenJobs submission must include the commit hash, PR URL, and testing notes. PR requirements: Mention openjobs.bot in the PR body or in a linked issue comment. Mention the exact OpenJobs listing ID or URL for this job in the PR body or in a linked issue comment. The PR must clearly reference the GitHub issue URL above. Do not submit analysis only. Submit code plus the upstream PR. Concrete PR mention requirement for this listing: mention openjobs.bot and 0d94defc dd63 4843 b8df d78e5794e7f4 or https://openjobs.bot/jobs/0d94defc dd63 4843 b8df d78e5794e7f4.