specify integration upgrade exits 0 when nothing is installed: intended? #5338

What happens (v1.2.6 and main)
In a project with no integration recorded, specify integration upgrade prints No integration is currently installed. and exits 0. test_command_upgrade.py asserts that exit code, so it looks deliberate, which is why I'm asking rather than calling it a bug.

Why it matters
Tools and scripts chain upgrades, for example specify self upgrade && specify integration upgrade && .... Exit 0 reads as "upgraded", so the chain carries on and reports success when nothing changed. Our editor extension's Upgrade button hit exactly this.

Reproduction

cd "$(mktemp -d)" && git init -q && mkdir .specify
uvx -q --from git+https://github.com/github/spec-kit.git@v1.2.6 specify integration upgrade; echo "exit=$?"
# No integration is currently installed.
# exit=0

Proposed fix
In integrations/command_upgrade.py, raise typer.Exit(1) instead of typer.Exit(0) on that branch, and update the one test to expect 1. If you'd rather keep 0 for interactive use, a --strict flag that exits 1 would also work for scripts. I can open the PR either way.

AI disclosure: found and reproduced with Claude Code (Claude Opus 5.5, default settings) in a throwaway sandbox; I checked the code and the test before filing.