feat(docker): exclude .iloom directory from Docker build context

[acreeger]

Problem

When building Docker images for dev server mode, the .iloom directory (containing config, prompts, metadata) is included in the build context. This is unnecessary — it bloats the context sent to the Docker daemon and could leak iloom-specific files into images.

Proposed Solution

Pipe a filtered tar archive to docker build via stdin instead of passing . as the build context:

tar -c --exclude='.iloom' -C /worktree . | docker build -t imageName -f ./Dockerfile -

In code, replace args.push('.') with args.push('-') and pipe a tar subprocess (with --exclude=.iloom) into docker's stdin:

const tar = execa('tar', ['-c', '--exclude=.iloom', '.'], { cwd: worktreePath })
await execa('docker', args, { stdin: tar.stdout, stdout: 'inherit', stderr: 'inherit' })

Why not .dockerignore?

• Requires creating/modifying a user-controlled file
• Would need cleanup logic and git status management
• Doesn't work if the project already has a .dockerignore that gets overwritten

Why not --ignore?

Docker CLI has no --ignore flag for inline ignore patterns.

Files to change

• src/lib/DockerDevServerStrategy.ts — buildImage() method
• src/lib/DockerManager.ts — buildImage() static method

Notes

• Verify execa v8 subprocess piping API (.pipe() or stdin option)
• Docker reads -f ./Dockerfile relative to the tar context, so existing -f usage should work unchanged
• stdio: 'inherit' for stdout/stderr must be preserved so build progress is visible