feat(update): show download progress and abort only stalled downloads - #15382

What

downloadVerifiedBinary (used for both full and patch downloads) now:

• shows a single, in-place progress line on a TTY: 42.1MB / 180.3MB (23%), 1.2MB/s, 1m50s left. Non-TTY output is unchanged.
• replaces the 15-minute deadline on the whole transfer with a stall timeout. The download aborts only when no bytes arrive for 60 seconds (Download stalled: no data received for 60 seconds). A slow but steady connection can now finish.

The stale-temp sweep used to rely on that 15-minute deadline: a .new/.patch temp older than it could not belong to a live download. Without a total limit that no longer holds, and on Windows a file's mtime may not change until its writer closes it. The sweep now also spares any temp whose updater pid (already in the file name) is still running, via procmgr.isPidRunning. The 15-minute age rule still applies to temps whose updater has exited, and to legacy names.

Why

On my network omp update printed Downloading omp-darwin-arm64… and nothing else for a long time, then in some cases failed with Timed out downloading release binary after 15 minutes. It's both annoying to never see any progress and wait for a very long timeout when target download is completely inaccessible.

Fixes #9499. Supersedes #9570, which no longer applies to main after the build-service/patch rewrite of the update path.

Testing

• End to end: built the binary from this branch (bun run build), copied it to a scratch directory first on PATH, and ran omp update --force (the branch reports the current release, 18.9.1). In a terminal the progress line updated in place through 197.7MB, then the build verified, installed and passed the version check. With output piped, the run printed the same lines as before this change and no progress.
• Smoke test against a local, throttled Bun server through real fetch: when the server stops sending halfway, the download aborts after about 62 seconds with the stall message and removes the partial file.
• Ran the same throttled download in a 40-column PTY: every progress frame is cut to 39 columns, so the line never wraps and each redraw replaces the previous one.
• bun test test/update-cli.test.ts: two fake-timer tests replace the old body-timeout test. A download receiving one byte every 20 seconds for minutes completes; a body that stops sending aborts after 60 seconds and leaves no file. Removing the stallTimer.refresh() call makes the first test fail. The sweep test now uses a pid that has exited for its orphaned temps (the old hard-coded 4242 could be a live process) and checks that an old temp owned by a running process survives. One unrelated test (overrides per-tool release age during actual mise upgrade resolution) fails on unmodified main in my environment too, because the local mise cannot resolve the github: tool.
• bun check passes (TypeScript and Rust).

• bun check passes
• Tested locally
• CHANGELOG updated with the required attribution (if user-facing; internal issue fixes use issue links, external contributions add the PR link and contributor credit after creation)