fix(dify): redact error event messages

[XnLemon]

Objective

Redact model-visible Dify agent error event messages for Phase2 redaction closure.

Completed Changes

• Route Dify sendErrorEvent ResponseError.Message through the shared platform redactor.
• Add regression coverage for Authorization, api_key, and Cookie leakage strings in Dify error events.
• Add table-driven coverage for token, secret, and password fields, plus a benign token limit exceeded case to guard against over-redaction.

Validation

• cd agent/dify && GOPROXY=https://goproxy.cn,direct go test ./...
• cd agent/dify && GOPROXY=https://goproxy.cn,direct go vet ./...
• git diff --check
• Subagent open-code-review first pass: 0 High / 0 Medium / 1 Low
• Subagent open-code-review final pass: 0 High / 0 Medium / 0 Low

Known Risks / Limitations

• The first Dify validation attempt hit proxy.golang.org download timeouts; reran successfully with GOPROXY=https://goproxy.cn,direct.
• This increment is scoped to Dify sendErrorEvent; remaining Phase2 model-visible error surfaces should continue in follow-up increments.

Follow-up Work

• Continue Phase2 closure by scanning remaining model-visible error and tool-result surfaces outside the agent-specific sendErrorEvent paths.

[coderabbitai]

Warning

Review limit reached

@XnLemon, you've reached your PR review limit, so we couldn't start this review.

Next review available in: 17 minutes

Enable usage-based reviews in Billing to review now. Otherwise, wait until the next included review is available.
You're only billed for reviews past your plan's rate limits ($0.25/file).

How can I continue?

After more reviews become available, a review can be triggered using the @coderabbitai review command as a PR comment. Alternatively, push new commits to this PR.

To avoid repeated limits, reduce automatic review volume by pausing incremental auto-reviews earlier, using label-based review opt-in, excluding WIP or generated PR titles, or requesting reviews manually when the PR is ready. If your team needs uninterrupted high-volume reviews, an organization admin can enable usage-based reviews.

How do review limits work?

CodeRabbit enforces per-developer PR review limits for each organization. Most developers receive the normal plan review availability.

For paid Pro and Pro+ PR reviews, CodeRabbit uses adaptive limits for sustained high-volume activity. When a developer's recent PR review activity reaches the 95th percentile or higher among CodeRabbit users, additional reviews become available more gradually as earlier reviews age out of the rolling window.

Please refer docs for additional details.

Review details

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro Plus

Run ID: 095e91a9-ea30-4605-bdad-96cbd2769ac6

📥 Commits

Reviewing files that changed from the base of the PR and between 361e2a4 and bb7678d.

📒 Files selected for processing (2)

• agent/dify/dify_agent.go
• agent/dify/dify_agent_test.go

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch codex/phase2-dify-error-event-redaction

---

_{Comment @coderabbitai help to get the list of available commands.}