chore(ruff): enable dictionary iteration checks

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This pull request was authored by a coding agent.

📝 Summary

• remove PERF403 and PLC0206 from the project-wide Ruff ignore list
• replace four manual dictionary-building loops with filtered comprehensions or dict.update
• iterate over dictionary items directly at seven sites instead of repeating indexed lookups
• preserve filtering, insertion order, and last-write-wins behavior

📋 Pre-Review Checklist

• For large changes, or changes that affect the public API: this change was discussed or approved through an issue, on Discord, or the community discussions (not applicable: small internal lint cleanup).
• Any AI generated code has been reviewed line-by-line by the human PR author, who stands by it.
• Video or media evidence is provided for any visual changes (not applicable: no visual changes).

✅ Merge Checklist

• I have read the contributor guidelines.
• Documentation has been updated where applicable, including docstrings for API changes (not applicable: no API changes).
• Tests have been added for the changes made (existing focused tests cover the behavior).

🧪 Testing

• uv run --group test pytest tests/_runtime/test_commands.py tests/_runtime/reload/test_module_watcher.py tests/_runtime/utils/test_set_ui_element_request_manager.py tests/_session/state/test_session_view.py (144 passed, 2 xpassed)
• uv run --group test pytest tests/_ast/test_app_config.py tests/_lint/test_validate_graph.py tests/_runtime/test_executor_evaluator.py tests/_runtime/utils/test_set_ui_element_request_manager.py tests/_server/ai/test_prompts.py tests/_utils/test_deep_merge.py (85 passed)
• make check

Written by gpt-5.6-sol on Codex

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Project	Deployment	Actions	Updated (UTC)
marimo-docs	Ready	Preview	Aug 28, 2026 12:21pm

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