Add a LeetCode Python solution

Turn an LC number (plus, usually, a draft the user already wrote) into a committed-quality Python solution file and its README row, in the shape the other ~826 files under leetcode_python/ already use.

Invocation: /lc-python <LC number> <pattern dir> — e.g. /lc-python 4038 Hash_table. A reference or draft solution pasted under the command is used as V0; with no draft, the draft is usually already in the contest scratch file (step 1).

Missing arguments are inferred, not asked about: the pattern dir from the technique the solution actually uses. Ask only if the number itself is missing or the dir is genuinely ambiguous.

Wrong skill? This one owns leetcode_python/ only. A Java solution goes to /lc-java — it files into leetcode_java/src/main/java/LeetCodeJava/ and updates the README row this skill created rather than adding a second one. If the user pasted Java, say so and switch rather than translating it to Python.