feat: implement configurable tool container home directory

- Add ToolType.home_directory column with default /home/user
- Add Alembic migration to add column, set existing rows, and rewrite
  /workspace to /home/user/{{WORKSPACE_NAME}} in legacy templates
- Add merge migration fc8f1a20cbf6 to resolve Alembic multiple heads
- Update manifest compiler to honor manifest.home_directory for HOME,
  WORKDIR, /workspace symlink, and default repo mount target
- Update legacy dockerfile/compose instance generation to use
  tool_type.home_directory
- Thread resolved home_dir through config profile and git mount expansion
- Generate entrypoint permission fixer to chown home/mounts at startup
- Update base.dockerfile with sudo/passwordless sudo for permission fixer
- Add unit tests for manifest compiler, instance service, and migrations
- Add placeholder integration test for container lifecycle
- Update openspec/tasks/home-path-expansion.md task checkboxes
- Update project maps for modified files

Quality gates: py_compile, ruff, mypy, pytest tests/unit (205 passed),
pytest tests/integration (110 passed, 35 skipped). Alembic round-trip
and container lifecycle integration tests require Docker/PostgreSQL.

apps/api/src/services/docker/compose.py

@@ -61,6 +61,19 @@ def render_compose_template(template: str, variables: dict[str, Any]) -> str:
     for key, value in variables.items():
         placeholder = f"{{{{{key}}}}}"
         result = result.replace(placeholder, str(value))
+
+    # Convenience aliases so legacy and migrated templates can use lowercase
+    # placeholders without changing every stored template.
+    aliases = {
+        "{{workspace_name}}": "WORKSPACE_NAME",
+        "{{home_directory}}": "HOME_DIRECTORY",
+    }
+    for alias_placeholder, key in aliases.items():
+        if alias_placeholder in result:
+            result = result.replace(
+                alias_placeholder, str(variables.get(key, "workspace"))
+            )
+
     return result