fix(documents): guard Unix-only resource import for Windows (#877)

`document_processors/_isolation.py` did an unconditional module-level
`import resource`, a POSIX-only stdlib module absent on Windows. It was
pulled into the API startup path via
`server/webdav.py -> utils/document_parser -> document_processors`, so
the MCP server failed to start on Windows since 0.101.2 with
`ModuleNotFoundError: No module named 'resource'`.

- Guard the import behind `sys.platform`; bind `resource = None` on
  win32. `_apply_mem_limit()` degrades to a logged no-op when the module
  is unavailable (the RLIMIT_AS cap is a Linux-pod safety measure, not a
  correctness requirement).
- Make the document-parser import in `server/webdav.py` lazy so server
  startup never loads the ingest document stack
  (document_processors -> pymupdf -> _isolation) at all -- it is only
  needed when a file is actually read and parsed. This both fixes #877
  and decouples the API layer from ingest-only deps.
- Add unit regressions for the no-op path and the win32 import guard.
- Add a cross-platform `package-smoke` CI job (ubuntu + windows) that
  installs the package isolated and runs the CLI, exercising the
  cli -> server -> webdav import chain that crashed in #877.

Fixes #877

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

nextcloud_mcp_server/server/webdav.py

@@ -13,10 +13,6 @@ from nextcloud_mcp_server.server.tag_exclusion import (
     get_excluded_file_paths,
     is_path_excluded,
 )
-from nextcloud_mcp_server.utils.document_parser import (
-    is_parseable_document,
-    parse_document,
-)
 
 logger = logging.getLogger(__name__)
 
@@ -115,6 +111,16 @@ def configure_webdav_tools(mcp: FastMCP):
 
         content, content_type = await client.webdav.read_file(path)
 
+        # Imported lazily so server startup never loads the document-parsing
+        # stack (document_processors -> pymupdf -> _isolation). That stack is an
+        # ingest-layer concern and, before this, broke Windows startup via a
+        # Unix-only ``import resource`` (#877). It is only needed when a file is
+        # actually read and parsed.
+        from nextcloud_mcp_server.utils.document_parser import (  # noqa: PLC0415
+            is_parseable_document,
+            parse_document,
+        )
+
         # Check if this is a parseable document (PDF, DOCX, etc.)
         # is_parseable_document() checks if document processing is enabled
         if is_parseable_document(content_type):