--throttle should take a float, not an int

[rolandwalker]

Description

Introduced in #1732.

Checklist

• I added this contribution to the changelog.md file.
• I added my name to the AUTHORS file (or it's already there).
• To lint and format the code, I ran

  uv run ruff check && uv run ruff format && uv run mypy --install-types .

[github-actions]

1. Medium: --throttle now accepts non-finite values (inf, -inf, nan) and passes them to sleep()
   At mycli/main.py:2161, switching to type=float allows click to parse inf/-inf/nan. Those values flow to mycli/main.py:2706:

   • nan / -inf raise at runtime (after entering batch execution)
   • inf can block indefinitely
     Action: validate at parse time (math.isfinite(value) and value >= 0) via a callback or constrained type.

2. Low: No regression tests for the behavior this PR changes
   I don’t see tests covering --throttle parsing/validation in test/test_main.py.
   Action: add CLI tests for:

   • --throttle 0.5 accepted and used
   • invalid values (nan, inf, negative) rejected with a clear CLI error before query execution.

No additional security issues were found beyond the non-finite input handling above.