refactor(skills): align MPI skills with Agent Skills best practices

The skill metadata had drifted: every SKILL.md name field lacked the
mpi- prefix, contradicting the directory names and the Agent Skills
specification. Descriptions were also missing negative triggers, making
it easy for the agent to load the wrong skill.

Rewrote the pdf-to-docx skill to follow progressive disclosure: the main
SKILL.md dropped from 318 lines to 80, with detailed code examples moved
to on-demand references. Added uv run instructions and /// script PEP 723
metadata so dependencies are declared inline and installed automatically.
Fixed the pptx skill's script paths and added CLI usage messages to both
pptx scripts and the normalize script.

Removed the empty self-review directory that was superseded by the unified
translation-review skill.

skills/mpi-chinese-text-normalize/scripts/normalize_breaks.py

@@ -1,3 +1,8 @@
+# /// script
+# requires-python = ">=3.9"
+# dependencies = []
+# ///
+
 """
 Fix extraneous line breaks in Chinese markdown files.
 
@@ -6,8 +11,9 @@ Three file patterns:
 2. Mostly-paragraph with stray breaks + outline TOC -> join broken lines, preserve list items
 3. Already fine -> skip (idempotent)
 
-Usage: python3 normalize_breaks.py <directory>
+Usage: uv run normalize_breaks.py <directory>
 """
+
 import re
 import sys
 from pathlib import Path
@@ -155,6 +161,9 @@ def process_file(filepath):
 
 
 def main():
+    if len(sys.argv) != 2:
+        print("Usage: uv run normalize_breaks.py <directory>", file=sys.stderr)
+        sys.exit(1)
     workdir = Path(sys.argv[1])
     files = sorted(workdir.glob('*.md'))