fix(worktree-cli): forward dev flags to vite and reuse existing branches

[rlueder]

Summary

Two small fixes that together make the end-to-end worktree flow —
precisa-worktree setup <branch> && precisa-worktree dev --detach —
actually work for the OSS sites (fhir-brasil, medbench-brasil,
datasus-brasil). Both issues surfaced while setting up dev servers to
visually verify the Header / OpenFooter migration.

1. `dev`: drop the `--` separator before script args

Invocation was:

```
pnpm --filter dev -- --port
```

Under pnpm 9 with a plain `"dev": "vite"` script, the `--` separator
is preserved in the spawned argv, so vite receives
`vite -- --port 4333` and silently ignores the port flag, falling back
to its default (4321). Removing the `--` forwards the flags directly
(`vite --port 4333`), which is what all existing service configs
(platform, OSS repos) expect.

Verified locally: `pnpm --filter @fhir-brasil/site dev --port 9998`
binds to 9998; `pnpm --filter @fhir-brasil/site dev -- --port 9998`
falls back to 4321.

2. `setup`: reuse an existing branch instead of erroring

`setup` always ran `git worktree add -b ... origin/main`,
which fails with `fatal: a branch named '' already exists`
whenever the branch was created previously (e.g. in the main worktree,
then pushed, then later promoted to a real feature worktree).

Now: detect the case via `git show-ref` against local +
`refs/remotes/origin/`, and fall back to
`git worktree add ` (without `-b`) to check out the
existing branch.

Test plan

• `pnpm turbo run build typecheck --filter=@precisa-saude/worktree-cli` passes
• Manually verified the flag-forwarding behavior with pnpm 9
• After merge + release, rerun `setup`/`dev` in fhir-brasil and medbench-brasil for the `feat/shared-header-footer` branches

[github-actions]

Automated Review — Round 1

Summary

The PR introduces a new utility function for checking branch existence and modifies the logic for adding git worktrees. While the changes improve functionality, there are performance considerations and potential issues with error handling.

Changes

• Modified arguments in spawnService function in dev.ts
• Added branch existence checking in setup.ts
• Adjusted logic for adding git worktrees in setup.ts

---

🔍 Found 2 suggestions (see inline comments)

Reviewed by OpenAI gpt-4o-mini (fallback) | 1,160 in / 184 out | $0.0003 — Round 1 of 2