Add per-project scope option and fix interactive sudo prompt

[peter-wagstaff]

Summary

• feat: Add scope option (shared | per-project) to isolate persistence data per dev container
• fix: Use sudo -n (non-interactive) to prevent password prompts that block container startup in environments without passwordless sudo

Motivation

When using agent-persistence across multiple projects, all containers share the same volume, which means conversation history, plugin configs, and cached setup state bleed between projects. The new per-project scope creates isolated subdirectories within the volume keyed by DEVCONTAINER_ID, so each workspace gets its own data while still sharing a single Docker volume.

Changes

• oncreate.sh / poststart.sh: Use sudo -n to fail silently instead of blocking on a password prompt; support DEVCONTAINER_ID-based subdirectory when scope is per-project
• install.sh: Pass SCOPE option through to the env file
• devcontainer-feature.json: Add scope option (default: shared for backwards compatibility), bump version to 1.4.0

Usage

  "features": {
      "ghcr.io/fjktkm/devcontainer-features/agent-persistence:1": {
          "scope": "per-project"
      }
  }

Note: per-project scope requires DEVCONTAINER_ID in the project's containerEnv because ${devcontainerId} substitution is not supported in feature

containerEnv metadata:

  "containerEnv": {
      "DEVCONTAINER_ID": "${devcontainerId}"
  }

Without this, the feature falls back to shared scope.

Backwards Compatibility

Default behavior is unchanged, scope defaults to shared, which uses the volume root exactly as before.