bug: Bun runtime deploy fails with workspaces in package.json ("Workspace not found") #3272

Description

When using runtime: 'bun' in trigger.config.ts, deploying a project that has "workspaces" in package.json fails with:

error: Workspace not found "frontend"
    at /app/package.json:50:5

The same project deploys successfully with runtime: 'node-22'.

Root Cause

The generated Containerfile copies only package.json before running bun install:

COPY --chown=bun:bun package.json ./          # Only root package.json
RUN bun install --production --no-save        # Bun validates workspaces strictly → ERROR
COPY --chown=bun:bun . ./                     # Workspace dirs arrive here, too late

npm/node tolerates missing workspace directories during install (warns but continues).
Bun strictly validates that all referenced workspaces exist and exits with an error if they don't.

Reproduction

1. Have a package.json with workspaces:

{
  "workspaces": ["frontend"]
}

2. Set runtime: 'bun' in trigger.config.ts:

export default defineConfig({
  project: 'my-project',
  runtime: 'bun',
});

3. Run trigger deploy → build fails at the bun install step.

4. Change to runtime: 'node-22' → build succeeds.

Environment

• CLI version: 4.4.1
• Cloud version: 4.4.3
• Bun version in image: 1.3.3 (imbios/bun-node:1.3.3-20-slim)
• OS: Ubuntu (GitHub Actions CI)

Suggested Fix

When runtime: 'bun', the Containerfile should handle workspaces before bun install. Some options:

1. Copy workspace package.json files alongside the root package.json before install:

   COPY --chown=bun:bun package.json ./
   COPY --chown=bun:bun frontend/package.json ./frontend/
   RUN bun install --production --no-save

2. Strip the workspaces field from package.json before running bun install:

   COPY --chown=bun:bun package.json ./
   RUN node -e "const p=JSON.parse(require('fs').readFileSync('package.json','utf8'));delete p.workspaces;require('fs').writeFileSync('package.json',JSON.stringify(p,null,2))"
   RUN bun install --production --no-save

3. Allow build extensions to inject Containerfile instructions between COPY package.json and RUN bun install (currently addLayer only appends after the main build steps).

Workaround

Use runtime: 'node-22' instead of 'bun'. With processKeepAlive: true, warm starts are 100-300ms regardless of runtime, so the cold start difference is negligible for most workloads.