chore: prep 0.7.5 metadata and integration literal cleanup

[rlippmann]

What changed

• Bumped package version from 0.7.4 to 0.7.5.
• Updated lockfile via uv lock for the version bump.
• Replaced remaining low-risk semantic decision literals in integration host code with exported decision constants.
• Updated OpenWebUI example frontmatter metadata:
  • open_webui_pipe.py: version: 0.9.3
  • open_webui_pipe_with_preprocessor.py: version: 0.9.3

Why

• Keep release metadata aligned for the 0.7.5 release.
• Reduce copy-paste drift in user-facing integrations by preferring exported constants for semantic decision values.
• Keep integration examples consistent with the current helper/constants guidance.

Checklist

• pre-commit run (uv run pre-commit run --all-files)
• tests pass (uv run pytest)