Post-release maintenance: dependencies, onboarding, and examples

[TimeLordRaps]

Summary- update the optional RISC Zero host from rand 0.8.5 to 0.8.6 and regenerate the workspace lock file;- document and regression-test why the transitive tracing-subscriber 0.2.25 advisory is not reachable in the exact pinned build: both lock files enable only tracing-core, and neither host nor guest initializes terminal formatting;- add a 90-second README mental model, a task-oriented starting route, and a collapsed exact maturity matrix so newcomer orientation no longer competes with reviewer detail;- move non-normative research sources from the visually prominent root experiments/ directory to examples/experimental_profiles/, while retaining the stable public Pages route /experiments/;- keep issue #21 closed as superseded by the published VSTD 1.2.0 release sequence.## Dependency alert disposition| Alerts | Treatment ||---|---|| rand in the RISC Zero host manifest and workspace lock | Updated to the first patched 0.8 release, 0.8.6. GitHub's default-branch alerts remain visible until this pull request is merged. || tracing-subscriber in the two RISC Zero lock files | Dismissed as not_used only for the exact pinned feature graph. The vulnerable terminal-formatting mechanism is absent; the boundary expires if dependency features, lock files, RISC Zero, or source initialization changes. |This does not claim that the transitive package version is generally safe. It records the narrower proposition that the affected mechanism is not compiled or initialized by this example at this coordinate.## Validation- python -m pytest -q — 555 passed, 38 skipped- focused presentation, experimental-profile, and ZIZK tests — 65 passed- python scripts/check_presentation.py — passed- python scripts/build_reference.py --check — passed- python scripts/build_experiment_index.py --check — passed- python scripts/check_terminology.py — passed- python -m compileall -q src scripts — passed- zero-third-party-dependency import — version 1.2.0 loaded- documentation build — 43 navigable pages rendered- Ubuntu 24.04 under Windows Subsystem for Linux: cargo check --workspace --locked and cargo test --workspace --locked — passed with the pinned Rust 1.97 toolchainThe native Windows Rust check is not claimed: this host's Visual Studio link.exe exits with 0xc000007b. The same exact source and lock files compiled successfully in Ubuntu.## Exact-head hosted checks

repository-checks run 33567149118 completed successfully at exact head f8ab4bc7872c06782d326336309a32869ba9aac9. The Python 3.10-3.13 matrix, bounded branch coverage, CodeQL, presentation and Pages build, installed-wheel smoke test, artifact seal path, Supply Chain Integrity, Transparency, and Trust cryptography, Linux and Windows release-integrity builds, cross-platform release reproducibility, and aggregate conformance gate all passed.

Compatibility and claim boundary- no VSTD wire, schema, numbered-profile, public Python interface, or release metadata changes;- version 1.2.0 remains the released version;- governing ZIZK artifact-first architecture remains outside the experimental source grouping;- the generated GitHub Pages path /experiments/ remains stable;- the moved experiment manifest is re-bound to the exact moved design-note bytes and passes repository manifest verification.## Commits- 891b29a2 — dependency and advisory boundary- f8ab4bc7 — newcomer presentation and experiment-source hierarchyBoth commits are unattended OpenPGP-signed and must appear GitHub Verified.## Review gate- [ ] Human review confirms the newcomer path is materially clearer without weakening the exact maturity and claim boundaries.- [ ] Human review confirms the transitive advisory dismissal remains bounded to the exact compiled feature graph.No merge, tag, release, publication, or deployment is authorized by this pull request description.