release: cut v0.75.0

[trendvidia]

Summary

Fifth and final PR of the v0.72–v0.75 cpp catch-up. Bumps `project(... VERSION ...)` from `0.70.0` to `0.75.0` and rolls the [Unreleased] CHANGELOG entries into a dated [0.75.0] section.

This release closes the gap with the rest of the `protowire-*` stack. All four PXF v0.72-series features now ship in the C++ port, landed across PRs #9 / #10 / #11 / #12 / #13:

• `@` / `@entry` / `@table` directive grammar (pxf: parser-side @<name>/@entry/@table directive grammar #9) — parser + fast path
• Schema reserved-name validator (pxf: schema reserved-name validator (draft §3.13) #11) — draft §3.13, `UnmarshalOptions::skip_validate` opt-out
• `Result::Directives()` / `Result::Tables()` (pxf: Result::Directives() / Result::Tables() accessors #12) — accessors expose parsed directive shape after `UnmarshalFull`
• `TableReader` streaming + `Scan` / `BindRow` (pxf: TableReader streaming + Scan/BindRow per-row binding #13) — CSV-replacement workload, working-set bounded by largest single row

The cpp 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 and create the GitHub release:

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

Test plan

• All 218 tests pass locally with the bumped version
• CI green (clang-format, all matrix jobs, CodeQL)

[codecov-commenter]

⚠️ Please install the to ensure uploads and comments are reliably processed by Codecov.

Codecov Report

✅ All modified and coverable lines are covered by tests.

📢 Thoughts on this report? Let us know!