chore: release 0.3.0

[lostmygithubaccount]

Summary

Releases 0.3.0 — accumulates this cycle's work into a coherent minor bump. Minor (not patch) because of one breaking change in `dkdc-draw-core`'s public API surface.

Contents

PR	Kind	Summary
#35	feat	Arrow snap-to-shape connection points
#36	docs	CONTRIBUTING.md + README badges
#37	test	Integration tests for draw-core public API
#38	docs	Rust + Python hello-world examples
#39	docs	CHANGELOG.md scaffolding
#40	chore	Surgical clippy opt-ins workspace-wide
#41	docs	Sample gallery (5 drawings × json/svg/png)
#42	refactor	Breaking: pub → pub(crate) demotions
#43	test	Python test coverage 5 → 27

Breaking changes (from #42)

These items moved from `pub` to `pub(crate)` in `dkdc-draw-core` — any external caller referring to them by name will fail to compile against 0.3.0:

• `geometry::ARROWHEAD_LENGTH`, `ARROWHEAD_ANGLE`, `HACHURE_LINE_WIDTH`
• `geometry::normalize_bounds`, `compute_arrowhead`, `generate_hachure_lines`
• `geometry::ArrowheadPoints`, `HachureLine` (structs + fields)
• `point::Bounds::from_points`

Migration guide

• `Point::distance_to` and `Bounds::intersects` remain public — recommended as the geometry vocabulary for external callers.
• `geometry::normalize_bounds` → inline two-line reduction: `let (nx, ny) = (x1.min(x2), y1.min(y2)); let (w, h) = ((x1 - x2).abs(), (y1 - y2).abs());`
• `Bounds::from_points` → construct with `Bounds::new(x, y, w, h)` from your own min/max reduction over the points.
• Arrowhead / hachure helpers: no public alternative is shipping yet. Open an issue if you need these and we'll carve out a stable API.

Full details in `CHANGELOG.md`.

Files changed

• Version bump across all 7 packages: `pyproject.toml` + 6 `Cargo.toml` + 3 lockfiles (via `bin/bump-version --minor`).
• `CHANGELOG.md`: [Unreleased] → [0.3.0] with breaking-change callout + migration notes; compare-link anchors updated.

Test plan

• `bin/bump-version --minor` applied cleanly (guards pass)
• `bin/check` green (rust + python + clippy + wasm-pack all pass against 0.3.0)
• `bin/test` green (rust + 27 python tests all pass)
• Package metadata audit: all 7 packages at 0.3.0, all have name/description/authors/license/repository/homepage

Publish gating

This PR lands the release state but does not publish to crates.io or PyPI. Cody decides publish timing — tagging `v0.3.0` triggers the existing release workflows (`.github/workflows/release-{rust,python,github}.yml`).

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