bootdev status intermittently fails: "failed to fetch latest version" #196

Summary

bootdev status intermittently fails its version check with:

Unable to check version status
Error: failed to fetch latest version

The same code path runs on every command via version.FetchUpdateInfo, so the flakiness affects more than just status.

Reproduction

Runs are non-deterministic — on my network this reproduces roughly 1 in 4 invocations:

$ for i in $(seq 1 8); do bootdev status 2>&1 | grep -E 'up to date|failed'; done
CLI up to date (v1.29.6)
CLI up to date (v1.29.6)
CLI up to date (v1.29.6)
Error: failed to fetch latest version   <-- intermittent
CLI up to date (v1.29.6)
...

Root cause

version.getLatestVersion() fetches @latest from the Go module proxy. Instrumenting the swallowed error shows the real cause is a transient connection drop to proxy.golang.org:

Get "https://proxy.golang.org/github.com/bootdotdev/bootdev/@latest": read tcp ...:443: read: connection reset by peer

The function has no resilience to this:

• No retry — a single connection reset fails the whole check.
• No effective fallback — the proxy list is [proxy.golang.org, direct], but direct is (correctly) skipped because @latest can't be fetched from it over HTTP, leaving proxy.golang.org as the only source.
• No timeout on http.Get, so a stalled connection can hang.
• The underlying error is swallowed and the HTTP status is never checked, so the user only ever sees the generic failed to fetch latest version message.

Proposed fix

#195 — retry transient proxy failures with backoff, add a client timeout, validate the HTTP status / response, and wrap the underlying error so the real cause is surfaced. Includes httptest-based unit tests.