fix: pi container repo mount target and npm update permissions

- Add Alembic migration to update built-in pi-agent manifest:
  * repo mount target from /workspace to ~/{{WORKSPACE_NAME}}
  * keep /workspace as compatibility symlink via working_dir
  * update startup chown target to $HOME/$WORKSPACE_NAME
- Pass REPO_NAME and WORKSPACE_NAME to compile_compose from instance_service
- Substitute {{WORKSPACE_NAME}} in manifest mount targets and expose it as
  a container env var so the entrypoint can create the /workspace symlink
- Generate entrypoint workspace symlink from runtime WORKSPACE_NAME env var
- Install npm_global packages into {home_dir}/.npm-global with PATH so the
  non-root container user can update global packages
- Update manifest compiler unit tests for the new behavior

Quality gates:
- pytest tests/unit: 207 passed
- ruff: clean on changed files
- mypy: clean on changed files
- alembic heads: single head

apps/api/src/services/build/manifest_compiler.py

@@ -143,13 +143,6 @@ def compile_dockerfile(manifest: dict) -> str:
         lines.append("    rm -rf /var/lib/apt/lists/*")
         lines.append("")
 
-    # NPM global packages
-    npm_packages = manifest.get("packages", {}).get("npm_global", [])
-    if npm_packages:
-        pkg_list = " ".join(shlex.quote(p) for p in npm_packages)
-        lines.append(f"RUN npm install -g {pkg_list}")
-        lines.append("")
-
     # Pip packages
     pip_packages = manifest.get("packages", {}).get("pip", [])
     if pip_packages:
@@ -161,6 +154,7 @@ def compile_dockerfile(manifest: dict) -> str:
     user = manifest.get("user")
     home_dir = get_manifest_home_dir(manifest)
     workspace_name = manifest.get("workspace_name", "{{WORKSPACE_NAME}}")
+    npm_prefix = ""
     if user:
         name = user["name"]
         uid = user["uid"]
@@ -195,6 +189,20 @@ def compile_dockerfile(manifest: dict) -> str:
         )
         lines.append("")
 
+        # NPM global packages: install into a user-writable prefix so the
+        # container user can update global packages without touching
+        # /usr/lib/node_modules (which is owned by root).
+        npm_packages = manifest.get("packages", {}).get("npm_global", [])
+        if npm_packages:
+            pkg_list = " ".join(shlex.quote(p) for p in npm_packages)
+            npm_prefix = f"{home_dir}/.npm-global"
+            lines.append(
+                f"RUN mkdir -p {npm_prefix} && "
+                f"npm install -g --prefix {npm_prefix} {pkg_list}"
+            )
+            lines.append(f"ENV PATH={npm_prefix}/bin:$PATH")
+            lines.append("")
+
     # Build scripts
     build_scripts = manifest.get("scripts", {}).get("build", [])
     for script in build_scripts:
@@ -287,8 +295,6 @@ def compile_entrypoint(manifest: dict) -> str:
 
     user = manifest.get("user")
     home_dir = get_manifest_home_dir(manifest)
-    workspace_name = manifest.get("workspace_name", "{{WORKSPACE_NAME}}")
-    workspace_target = f"{home_dir}/{workspace_name}"
 
     # Permission fixer preamble: run as root when possible, else fall back to
     # passwordless sudo configured in the Dockerfile.
@@ -315,7 +321,8 @@ def compile_entrypoint(manifest: dict) -> str:
         lines.append(f"USER_UID='{uid}'")
         lines.append(f"USER_GID='{gid}'")
         lines.append(f"HOME_DIR='{home_dir}'")
-        lines.append(f"WORKSPACE_TARGET='{workspace_target}'")
+        lines.append('WORKSPACE_NAME="${WORKSPACE_NAME:-workspace}"')
+        lines.append('WORKSPACE_TARGET="${HOME_DIR}/${WORKSPACE_NAME}"')
         lines.append("")
         lines.append("fix_owner() {")
         lines.append("    local path=\"$1\"")
@@ -343,8 +350,13 @@ def compile_entrypoint(manifest: dict) -> str:
             target = mount.get("target")
             if not target:
                 continue
-            # Expand any ~/$HOME placeholders in the mount target.
-            expanded = target.replace("~", home_dir).replace("$HOME", home_dir)
+            # Expand any ~/$HOME placeholders and the runtime workspace name
+            # in the mount target so ownership is fixed at container startup.
+            expanded = (
+                target.replace("~", home_dir)
+                .replace("$HOME", home_dir)
+                .replace("{{WORKSPACE_NAME}}", "${WORKSPACE_NAME}")
+            )
             if expanded.startswith(home_dir) and not mount.get("readonly", False):
                 lines.append(f'fix_owner "{expanded}"')
         lines.append("")
@@ -409,6 +421,12 @@ def compile_compose(manifest: dict, variables: dict[str, Any]) -> str:
     if env:
         service["environment"] = dict(env)
 
+    # Expose the workspace/repo name so the entrypoint can finalize the
+    # /workspace compatibility symlink at container startup.
+    if "environment" not in service:
+        service["environment"] = {}
+    service["environment"]["WORKSPACE_NAME"] = workspace_name
+
     # Merge extra env from config
     extra_env = variables.get("EXTRA_ENV", {})
     if extra_env:
@@ -426,6 +444,7 @@ def compile_compose(manifest: dict, variables: dict[str, Any]) -> str:
         if mount.get("source_type") == "repo":
             has_explicit_repo_mount = True
         target = expand_container_path(mount["target"], home_dir)
+        target = target.replace("{{WORKSPACE_NAME}}", workspace_name)
         readonly = ":ro" if mount.get("readonly", False) else ""
         volumes.append(f"{source}:{target}{readonly}")