The install script crashed silently on repeated `--local` runs due to
three issues:
1. `REPO_URL` includes `.git` suffix which returns 404 when used for
GitHub releases API — `grep` found no match, exited 1, and
`set -euo pipefail` killed the script with no error message.
2. `multica version` outputs "multica 0.1.26 (commit: ...)" but the
version comparison used the full string, so it never matched the
release tag and always attempted unnecessary upgrades.
3. Interrupted previous clones left a non-empty directory without
`.git/`, causing `git clone` to fail on retry.
When multica CLI is already installed, the install script now checks
for a newer version on GitHub Releases and upgrades automatically.
Homebrew installs use `brew upgrade`; binary installs re-download
the latest release. If already up to date, it skips.
After installing via `curl | bash` (default/cloud mode) or running
`multica setup` without a local server, the CLI config could retain
stale localhost URLs from a previous `multica config local` or
`--local` install. This caused `multica login` to connect to
localhost instead of multica.ai.
Fix: explicitly write cloud URLs (api.multica.ai / multica.ai) to
the config in both the install script's cloud mode and the setup
command's cloud fallback path.
