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>

tests/unit/test_pdf_parse_isolation.py

@@ -14,6 +14,7 @@ or depend on the sample files).
 """
 
 import resource
+import sys
 
 import anyio
 import anyio.to_process
@@ -161,6 +162,41 @@ def test_apply_mem_limit_is_applied_once(monkeypatch):
     assert len(calls) == 1  # second call is a no-op
 
 
+# --- Windows / no-``resource`` platform compatibility (#877) -----------------
+
+
+def test_apply_mem_limit_noop_when_resource_unavailable(monkeypatch):
+    """On a platform without ``resource`` (e.g. Windows) the cap is skipped.
+
+    Regression for #877: ``resource`` is Unix-only, so ``_apply_mem_limit`` must
+    degrade to a no-op (rather than crash) when the module is unavailable.
+    """
+    monkeypatch.setattr(_isolation, "_MEM_LIMIT_APPLIED", False)
+    monkeypatch.setattr(_isolation, "resource", None)
+    _isolation._apply_mem_limit(1536)  # must not raise
+    assert _isolation._MEM_LIMIT_APPLIED is True
+
+
+def test_isolation_imports_on_windows_without_resource(monkeypatch):
+    """Importing ``_isolation`` on Windows must not crash on ``import resource``.
+
+    Regression for #877: a module-scope ``import resource`` raised
+    ``ModuleNotFoundError`` on Windows and took down server startup. With
+    ``sys.platform == 'win32'`` the module must import cleanly and bind
+    ``resource`` to ``None``.
+    """
+    import importlib
+
+    monkeypatch.setattr(sys, "platform", "win32")
+    monkeypatch.delitem(
+        sys.modules,
+        "nextcloud_mcp_server.document_processors._isolation",
+        raising=False,
+    )
+    mod = importlib.import_module("nextcloud_mcp_server.document_processors._isolation")
+    assert mod.resource is None
+
+
 # --- PyMuPDF processor wiring ------------------------------------------------