fix: avoid literal {{WORKSPACE_NAME}} directories in built images

When a manifest mount target uses ~/{{WORKSPACE_NAME}}, the Dockerfile was
building a literal directory named {{WORKSPACE_NAME}} into the image and
creating a broken /workspace symlink. The runtime mount then created the
correct repo-named folder alongside the placeholder folder.

- Only create static mount target directories in the Dockerfile; skip any
  target containing {{WORKSPACE_NAME}}
- Only create the /workspace compatibility symlink at image-build time when
  the workspace name is known; otherwise let the entrypoint create it from
  the WORKSPACE_NAME environment variable
- Update unit tests to cover both build-time workspace names and runtime
  placeholders

Quality gates:
- pytest tests/unit: 211 passed
- ruff: clean on changed files
- mypy: clean on changed files

apps/.pi-map.index.md

@@ -2,7 +2,7 @@
 dir: apps
 
 ## role
-Contains the deployable application entry points and executable configurations for the project.
+Contains the main deployable application modules that compose the complete system.
 ## parent
 index: ./.pi-map.index.md
 map: ./.pi-map.md