fix(installer): forward selected clients

[ketpatil77]

What does this PR do?

Fixes #1753 by forwarding install.sh --clients selections to the downloaded binary's installer.

• Supports both --clients=claude,codex and --clients claude,codex.
• Preserves --skip-config behavior.
• Rejects unknown options and unexpected positional arguments instead of silently ignoring them.
• Extends the installer smoke test with detected Claude and Codex clients, selects only Claude, and verifies Codex remains untouched.

Validation

• bash -n install.sh
• bash -n scripts/smoke-test.sh
• install.sh --help exposes --clients
• Unknown-option parser check rejects unsupported flags
• git diff --check

Full release-artifact smoke test was not run locally because it requires the repository's built release fixture.

Checklist

• Every commit is signed off (git commit -s) — required, CI rejects unsigned commits (DCO, see CONTRIBUTING.md)
• Tests pass locally (make -f Makefile.cbm test)
• Lint passes (make -f Makefile.cbm lint-ci)
• New behavior is covered by a test (reproduce-first for bug fixes)

[github-actions]

Thanks for opening this — it has been seen, and it is queued.

This note is automated, but it is not a brush-off: it exists so you know where your PR stands instead of having to guess from silence.

Current review status: working through a backlog. 0.9.1-rc.1 is out, so the release freeze that held reviews is over — but it left a large queue of open pull requests behind it, and we are reading through them oldest-first. The background is in discussion #1144.

What that means for this PR, concretely:

• It will not be closed for inactivity. No stale bot touches pull requests here.
• It may still sit a while before a human reads it. That is on us, not on you.
• Older PRs are read first, so a recent one is not being skipped — it is behind a queue.

Things that will genuinely speed it up whenever review does happen:

• Keep it rebased on main — the tree is moving quickly right now, and a conflicting branch cannot be reviewed as the diff you intended.
• Get CI green, or say which failures you believe are pre-existing.
• Keep the change to one claim. Bundled features and refactors get split before they get merged, which costs you a round trip.
• Every commit needs a sign-off (git commit -s) — CI enforces DCO.

If this fixes a bug, a reproduction we can run is worth more than a description of the symptom.

Thanks for contributing, and sorry in advance for the wait.