Take multidict 6.9.1

[vvillait88]

Summary

Takes multidict 6.9.1, a transitive patch released after the day's dependency sweep. Lock-only; no manifest change.

Type of change

• Bug fix (no breaking change)
• New feature (no breaking change)
• Breaking change (existing callers must update)
• Docs, tests, or internal maintenance only

Public API

None.

Test plan

uv lock --upgrade-package multidict, then every CI step run locally: uv sync --all-extras --all-groups, ruff check, ruff format --check, ty check (package and examples), vulture, and pytest (1869 passed, 4 skipped, 95.37% coverage against the 95% floor).

Checklist

• Tests cover the new behavior, and the suite passes locally (no new behavior; existing suite passes)
• Lint, format, and type checks pass
• Docs and README examples updated if the public surface changed (not changed)
• No secrets, credentials, or personal data in the diff or the tests