Pin the bundled winappcli version (or detect version skew) instead of always downloading `latest`

Problem

scripts/download-cli.ps1 defaults to downloading the latest winappcli release, but the extension's command surface is written against a specific CLI version. Today that means the extension ships a 0.6.x CLI behind a UI designed for ~0.3.1 — the version skew is invisible and unbounded in both directions.

The reverse direction is the dangerous one: as we add flags for newer CLI features, an extension build paired with an older CLI will emit flags that don't exist and fail at runtime with a raw CLI parse error.

Why it matters now

The winapp run project-mode work adds --project, --configuration, --arch, --framework, --runtime, --property, --no-build, and --no-restore — all of which are 0.6.x-only. If a user's bundled CLI predates them, project mode fails with an unhelpful error and no indication that a version mismatch is the cause.

Options

• Pin the tag in download-cli.ps1 to the version the extension was developed and tested against, and bump it deliberately alongside UI changes. npm run download-cli:latest stays available for local testing.
• Probe winapp --version once at activation and degrade the UI (hide project-mode entries, disable new options) when the CLI is older than required — more forgiving for users who point the extension at their own CLI build, but more machinery.
• Possibly both: pin for the shipped default, probe as a safety net.

Acceptance

Either the bundled CLI version is deterministic for a given extension version, or the extension detects a too-old CLI and reports it as a version mismatch rather than surfacing a raw argument-parsing failure.

Start with scripts/download-cli.ps1 and the extension activation path; compare the bundled download behavior with the CLI version used by the command surface. The issue notes that npm run download-cli:latest remains for local testing. Done when a shipped extension has a deterministic compatible CLI, or reports a clear version mismatch before unsupported arguments fail.