docs(tests): clarify report key behavior

[ischolten]

Summary

• clarify that --key identifies report uploads, not split timings
• explain when to use a distinct value for multiple report uploads from one job

Verification

• gofmt -d pkg/cmd/tests/run.go
• go test ./...

---

Note

Low Risk
Documentation-only change to a CLI flag description; no runtime behavior changes.

Overview
Updates the --key flag help text on depot tests run so it matches how the command actually behaves.

The description now calls it a report invocation key (still defaulting to GITHUB_ACTION or a default), tells users to set a distinct value when one job uploads reports more than once, and explicitly states that --key does not affect split timings (those use --split-key).

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[cursor]

Approved: Cursor Bugbot and Cursor Security Agent both completed successfully with no findings requiring human review. No reviewers assigned.

  

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