docs: unify Hyper onboarding for scientists and developers

[bregydoc]

Hyper's onboarding was split across two overlapping documentation PRs, with the main README mixing first-run instructions and detailed reference material. This consolidates #10 and #11 into one change: readers can try the prebuilt viewer, run a complete Python example, or integrate the Rust core from clearly named entry points.

Lead with the native viewer demo and the correct uvx --python 3.12 --from hypergraph-viz-viewer hyper command. Explain distribution/import/executable names, build a self-contained Python example with overlapping coauthorship groups, and provide a complete Rust layout example. Keep pip and source builds available, and preserve the expanded viewer reference while aligning its setup with the Python and desktop package guides.

For scientific use, distinguish HIF interchange from viewer compatibility, explain approximate hulls and current notebook limits, and link measured benchmarks and reproduction instructions. README research documents ten comparable projects with pinned primary sources and traces the editorial choices to the resulting README.

Validation:

• Ran the standalone published viewer's version command and a fresh CPython 3.12 uv project install from PyPI; confirmed both companion packages are 0.1.2 and checked project CLI help/version.
• Executed the exact README Python script with a headless process substituted for the viewer executable; checked overlapping memberships, HIF save/reload/round-trip, native conversion, and launcher cleanup. A graphics window was not exercised.
• Compiled and ran the exact Rust snippet against the local core (4 layout nodes) and ran the locked offline project_scene example.
• Checked 35 local links/anchors, code fences, four Python blocks, the native JSON membership references, ten pinned research sources, and git diff --check.

Supersedes #10 and #11. Application code and package versions are unchanged.