fix(release): rebaseline workshop-rs on release-plz and dist

[Teakowa]

Summary

• return release-plz to its standard push-to-main flow for Release PR maintenance, crates.io publication, and the single canonical vX.Y.Z tag;
• replace the repository-maintained five-platform GitHub Release state machine with dist 0.32;
• keep the five existing CLI targets, .tar.gz / .zip archive formats, SHA-256 checksums, and catalog-identity.json as a dist extra artifact;
• keep the already-proven CARGO_REGISTRY_TOKEN path in this change; crates.io Trusted Publishing is a separate follow-up after the external publisher configuration is verified.

Why

The current release pipeline has grown into a custom release orchestrator around release-plz: the release command runs from a merged-PR detached checkout, #54 has to synthesize a branch/upstream just to satisfy release-plz's Git context, and repository YAML separately owns tag creation, draft/published GitHub Release state, asset completeness, and partial-state recovery. Recent fixes #50, #51, and #54 are different symptoms of that same ownership problem.

This PR removes that state machine instead of adding another recovery condition.

Ownership contract

release-plz
  -> version / Release PR
  -> crates.io publication
  -> canonical vX.Y.Z tag

dist
  -> PR release plan
  -> five-platform workshop-rs-cli builds
  -> archive checksums
  -> catalog-identity.json
  -> GitHub Release with the complete artifact set

release-plz does not create the GitHub Release. dist does not decide crate versions or publish crates.io packages.

Distribution changes

The CLI targets remain:

• x86_64-unknown-linux-gnu
• aarch64-unknown-linux-gnu
• x86_64-apple-darwin
• aarch64-apple-darwin
• x86_64-pc-windows-msvc

Linux ARM64 moves from a repository-maintained cross-linker setup to GitHub's native ubuntu-24.04-arm runner.

dist emits standard per-archive .sha256 files, replacing the hand-built aggregate SHA256SUMS.txt. catalog-identity.json remains a release artifact generated from workshop-rs-cli version --json.

Removed custom orchestration

• pull_request.closed publication path;
• synthetic release-plz-release branch/upstream setup;
• manual gh api tag creation;
• repository-owned draft/published GitHub Release state machine;
• explicit published-release asset completeness recovery logic;
• hand-written five-platform archive/release workflow.

Rare partial external states are handled explicitly by maintainers instead of expanding the normal release path into a transaction coordinator across crates.io, Git, and GitHub Releases.

Validation

Validated on the final PR head:

• dist init --yes accepted the repository configuration and generated the checked-in Release workflow;
• the generated PR workflow runs dist plan successfully against the real PR merge ref;
• the five targets, native Linux ARM64 runner, SHA-256 configuration, and catalog-identity.json extra artifact are accepted by dist 0.32.0;
• stable Rust CI passes fmt, clippy, tests, and catalog validation;
• Rust 1.85.0 CI passes the same gates;
• the temporary generation diagnostic was removed;
• the final diff contains no second repository-owned tag/GitHub Release state machine.

The next real canonical tag remains the production end-to-end proof. No version is manufactured solely to test this migration.