Document EDT helper usage updates

[shai-almog]

Summary

• Expand the EDT developer guide to cover callSeriallyOnIdle, the callSeriallyAndWait timeout overload, and the invokeWithoutBlocking helpers and associated exception.
• Remove the obsolete docs/TODO.md checklist.

Testing

• Not run (documentation-only changes)

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https://chatgpt.com/codex/tasks/task_e_68fb1bf707e08331b81a18215fa1d6a8

[github-actions]

Developer Guide build artifacts are available for download from this workflow run:

• Developer Guide HTML package
• Developer Guide PDF
• AsciiDoc linter report
• Vale report
• Unused image report

Developer Guide quality checks:

• AsciiDoc linter: No issues found (report)
• Vale: 18605 alert(s) (2730 errors, 6302 warnings, 9573 suggestions) (exit code 1) (report)
• Image references: No unused images detected (report)