Update docx, pptx, and xlsx skills (#1447)

Add support for template formats (.dotx, .potx, .xltx) across validation
and the helper scripts.

Consolidate the shared office helpers into a single module, replacing the
pack/unpack pipeline with explicit zip/unzip steps. Extraction now rejects
symlink and path-traversal archive entries. Move run merging to a
standalone docx script, since it only ever applied to Word documents.

Fix the redlining validator so it compares against the original even when
a document has no tracked changes, which is when an untracked edit would
otherwise go unreported.

Provision a LibreOffice user profile per invocation so conversions work in
sandboxed environments.

Trim the skill docs to the guidance that earns its place.

skills/docx/scripts/office/soffice.py

@@ -4,20 +4,23 @@ sockets may be blocked (e.g., sandboxed VMs).  Detects the restriction
 at runtime and applies an LD_PRELOAD shim if needed.
 
 Usage:
-    from office.soffice import run_soffice, get_soffice_env
+    from office.soffice import run_soffice
 
-    # Option 1 – run soffice directly
     result = run_soffice(["--headless", "--convert-to", "pdf", "input.docx"])
 
-    # Option 2 – get env dict for your own subprocess calls
-    env = get_soffice_env()
-    subprocess.run(["soffice", ...], env=env)
+Call soffice through run_soffice, not through subprocess with get_soffice_env():
+the env dict carries the shim but names no user profile, and a non-root sandbox
+cannot bootstrap the default one -- soffice aborts with "User installation could
+not be completed" and converts nothing. get_soffice_env() stays public for the
+callers that build their own argv (they must pass -env:UserInstallation too).
 """
 
+import contextlib
 import os
 import socket
 import subprocess
 import tempfile
+from collections.abc import Iterable
 from pathlib import Path
 
 
@@ -32,9 +35,15 @@ def get_soffice_env() -> dict:
     return env
 
 
-def run_soffice(args: list[str], **kwargs) -> subprocess.CompletedProcess:
-    env = get_soffice_env()
-    return subprocess.run(["soffice"] + args, env=env, **kwargs)
+def run_soffice(args: Iterable[str], **kwargs) -> subprocess.CompletedProcess:
+    args = list(args)
+    with contextlib.ExitStack() as stack:
+        if not any(str(a).startswith("-env:UserInstallation") for a in args):
+            profile = stack.enter_context(
+                tempfile.TemporaryDirectory(prefix="lo_profile_", ignore_cleanup_errors=True)
+            )
+            args = [f"-env:UserInstallation={Path(profile).as_uri()}"] + args
+        return subprocess.run(["soffice"] + args, env=get_soffice_env(), **kwargs)