Summary

Third and final PR of the Python v0.72–v0.75 catch-up. Bumps `pyproject.toml` and `version` from `0.70.0` to `0.75.0` and rolls the [Unreleased] CHANGELOG entries into a dated [0.75.0] section.

Wraps the `protowire-cpp` v0.75.0 PXF v0.72-series feature set, landed across PRs #6 / #7:

• `pxf.Result.directives` / `pxf.Result.tables` (pxf: cpp pin to v0.75.0 + Result.directives/tables + validate_descriptor #6) — directive shape exposed after `unmarshal_full`
• `pxf.validate_descriptor` + `pxf.Violation` + `skip_validate` (pxf: cpp pin to v0.75.0 + Result.directives/tables + validate_descriptor #6) — schema reserved-name check (draft §3.13)
• `pxf.TableReader` + `pxf.bind_row` (pxf: TableReader streaming + bind_row per-row binding #7) — streaming `@table` consumption + per-row proto binding

The Python port jumps directly from v0.70.0 to v0.75.0, matching the active wire revision rather than re-tagging the intermediate versions Go and Java cut along the way.

Post-merge

After this PR lands, tag the merge commit. The `publish.yml` workflow fires on `v*` tag push and runs the full wheel matrix + PyPI publish via OIDC:

```bash
git tag -a v0.75.0 -m "v0.75.0 — PXF v0.72-series feature catch-up"
git push origin v0.75.0
```

The GitHub release page entry can be created from the tag once `publish.yml` finishes uploading wheels.

Test plan

• All 84 tests pass locally at the new version
• `protowire.version` reports `0.75.0`
• CI green (Linux / macOS / Windows × Python 3.10–3.13, cibuildwheel smoke, codeql)