feat(cli): add taskless share, a QR code for taskless.io

[theCodeDrift]

Adds taskless share: the Taskless banner over a scannable QR code for taskless.io, with `npx @taskless/cli` // www.taskless.io centered beneath it. For showing Taskless to someone in person.

• Link: https://www.taskless.io/?utm_source=cli&utm_medium=share&utm_content=<base version>. The version drops any prerelease/build suffix, so a nightly counts toward its release.
• Rendering: uqr (zero dependencies, ESM) encodes the QR code. With color, it is drawn dark-on-bright-white with explicit ANSI colors so it scans on light and dark themes. Without color (piped, NO_COLOR) it falls back to plain half blocks, which assumes a dark theme.
• Banner: wizard/intro.ts now exports renderBanner() and BANNER_WIDTH. renderIntro() is built from them, so the wizard's output is unchanged. The QR code and caption are centered on the banner's width.
• Caption: the caption hard-codes the release invocation on purpose. A nightly or local build should still send whoever scans it to the release. share.ts is therefore added to the no-unrouted-cli-invocation ignores, with a comment saying why.
• JSON: --json prints {"url": ...}.

Typecheck, lint, and the CLI tests pass locally. Not yet scanned on a phone.