fix(node-management): detach to canonical remote ref so remote-only branches install

[wangzhengzhuo05]

Summary

Fixes #2919. install_custom_node (action:install, source:git) with a ref that names a branch existing only as a remote-tracking branch (i.e. it is not the clone's default HEAD, so no local branch of that name exists) fails because:

git checkout --detach main
fatal: '--detach' cannot be used with '-b/-B/--orphan'

git's DWIM "create a local branch from origin/" kicks in for the bare name and conflicts with --detach. The install then errors and rolls back the clone.

What

In runGitCheckout (src/services/node-management.ts), after git fetch --all --tags and before the detach, a bare branch/tag name on the non-version path is canonicalized when it does not exist locally:

• If refs/heads/<name> or refs/tags/<name> exists locally (via gitShowRefExists) → keep the bare name (no DWIM risk).
• Else if refs/remotes/origin/<name> exists (via gitRemoteRefFor) → use that canonical fully-qualified ref path. git checkout --detach refs/remotes/origin/main never triggers DWIM.
• Else → keep the bare name; a genuinely missing ref fails with the normal git error (behavior unchanged).

The #1470 version-derived-channel branch (refFromVersion === true && isGitHeadChannel) is untouched. A probe failure (GitRefProbeError) is now rethrown instead of being misreported as a checkout error.

Why

The repository's clone default HEAD can differ from the requested branch (e.g. the repro repo in #2919 defaults to h3-community-r01, so main is remote-only after clone). The user then gets nothing installed and has to git clone -b main by hand.

Tests

• New #2919 test: ref: "main" with a remote-only main asserts the checkout uses ["-C", <dir>, "checkout", "--detach", "refs/remotes/origin/main"].
• The existing explicit-tag test (checkout --detach "v1.2.3") still passes unchanged, proving locally-present refs keep the bare name.
• Two cm-cli tests updated only to account for the new show-ref probe call (checkout assertions preserved in intent).

Verification

• npx vitest run src/__tests__/services/node-management.test.ts → 244 passed (243 baseline + 1 new).
• npm run build (tsc) → clean.
• Mutation check: with the canonicalization neutralized, the new #2919 test fails (checkout uses the bare main); restoring the fix makes it pass — the regression test genuinely guards the remote-only-branch path.

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[wangzhengzhuo05]

Closing this to keep the tracker clean \u2014 it has been sitting without review for several days. This is no reflection on the change itself: the fix and its local verification still stand. If the issue is still present and you would like the patch revisited, say the word and I will rebase it onto current main and re-open. Thanks for your time.