Add one-command public example verification

[cyou1314]

What changed

• Add verify-examples for a cross-platform, one-command report over every public plan, workflow, prompt-pack, QC-boundary, action, runtime-handoff, and JSON fixture.
• Keep the report privacy-safe: it uses relative paths and generic environment data, and tests the failed path for local-path leakage.
• Update the Windows launcher, quick start, contribution guide, feedback template, CI, and patch version to 0.2.1.

Why

A potential user previously had to run several commands (or a Windows-only batch file) to understand whether a clean checkout worked. The new command gives any tester one deterministic, copyable result before they decide whether to submit a real issue.

Developer impact

The command is standard-library-only and requires a cloned or extracted CineThread checkout. It validates contracts and dry-run handoffs only; it does not render, generate, open media, or claim final QC.

Validation

• 36 unit tests passed locally.
• Python compileall passed.
• Successful verification reported 11/11 checks.
• An invalid explicit --root now fails clearly rather than silently verifying a parent directory.
• git diff --check passed.