Description

spacetime dev saves "dev": { "run": "npm run dev" } to spacetime.json, but it always assumes npm regardless of the actual package manager used in the project.

Steps to Reproduce

1. Create a project using pnpm (with pnpm-lock.yaml and "packageManager": "pnpm@10.28.2" in package.json)
2. Run spacetime dev
3. Observe spacetime.json is modified to include "dev": { "run": "npm run dev" }

Expected Behavior

spacetime dev should detect the project's package manager by checking (in priority order):

1. packageManager field in package.json (corepack standard)
2. Lock file presence: pnpm-lock.yaml → pnpm, yarn.lock → yarn, bun.lockb → bun, package-lock.json → npm
3. Fall back to npm only if none of the above are found

The saved command should use the detected package manager: pnpm run dev, yarn dev, bun run dev, etc.

Actual Behavior

Always saves "npm run dev" regardless of the package manager. In a pnpm monorepo, this causes npm to be invoked (which may not have the correct dependencies hoisted) or fails entirely if npm is not the intended package manager.

Additional Context

• SpacetimeDB CLI version: v2.1.0
• The --server-only flag correctly skips client command detection, which is the current workaround
• This also affects initial project scaffolding via spacetime dev --template

Workaround

Use --server-only and run the client dev server separately, or manually edit spacetime.json after each run (since spacetime dev overwrites it on every invocation).

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