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/document_processors/_isolation.py

@@ -13,7 +13,7 @@ in its process pool.
 """
 
 import logging
-import resource
+import sys
 from pathlib import Path
 from typing import Any
 
@@ -21,6 +21,15 @@ import anyio
 import anyio.to_process
 from anyio import BrokenWorkerProcess
 
+# ``resource`` is a Unix-only stdlib module -- it does not exist on Windows, and
+# importing it unconditionally crashed Windows startup (#877). The RLIMIT_AS cap
+# it provides is a Linux-pod safety measure, not a correctness requirement, so on
+# platforms without it we fall back to a no-op (``resource is None``).
+if sys.platform == "win32":  # pragma: no cover - exercised only on Windows
+    resource = None
+else:
+    import resource
+
 logger = logging.getLogger(__name__)
 
 # Guard so the address-space limit is applied once per (reused) worker process.
@@ -44,10 +53,18 @@ def _apply_mem_limit(mem_limit_mb: int) -> None:
 
     Applied once per worker process. The hard limit is left untouched (we only
     lower the soft limit), and we never set a soft limit above the hard limit.
+
+    On a platform without the Unix-only ``resource`` module (e.g. Windows, see
+    #877) the cap is skipped -- the worker still runs, just without the
+    address-space limit.
     """
     global _MEM_LIMIT_APPLIED
     if _MEM_LIMIT_APPLIED or mem_limit_mb <= 0:
         return
+    if resource is None:
+        logger.debug("resource module unavailable; skipping RLIMIT_AS cap")
+        _MEM_LIMIT_APPLIED = True
+        return
     target = mem_limit_mb * 1024 * 1024
     soft, hard = resource.getrlimit(resource.RLIMIT_AS)
     soft_target = target if hard == resource.RLIM_INFINITY else min(target, hard)