coding-explain

You are running /coding-explain.

Step 1 — Resolve $ARGUMENTS

Take $ARGUMENTS as arg and resolve it to exactly one of four modes (check in this order):

1. Pattern — arg matches a pattern id in the coding-frameworks taxonomy (a ### <pattern> sub-section under ## Pattern taxonomy, e.g. two-pointers, sliding-window, dynamic-programming, backtracking, binary-search). Match on the slug OR the heading's key term — some ids map to compound headings (e.g. topological-sort → the "Graph: topological sort" subsection; bfs/dfs/hashing/heap similarly cover their compound headings). Set mode = pattern.
2. Problem — ${CLAUDE_PLUGIN_ROOT}/library/coding/<arg>.md exists (a library entry) OR $CLAUDE_PROJECT_DIR/coding/imported/<arg>.md exists (an imported entry; also strip a leading imported/ from arg and retry, so both <id> and imported/<id> resolve). Read it and hold its full content as topic_source. Set mode = problem.
3. Free prompt — arg is non-empty but matches neither a pattern nor an entry. Hold it verbatim as topic_prompt. Set mode = free.
4. Empty — arg is empty. Set mode = list.

If mode = list: load the coding-frameworks skill and list every ### <pattern> from its ## Pattern taxonomy; then Read the frontmatter id and difficulty of each ${CLAUDE_PLUGIN_ROOT}/library/coding/*.md and present the problems as a numbered list grouped by difficulty. Ask the user to pick a pattern or a problem, then re-resolve their answer through this step.

Step 2 — Load the skill

Before teaching anything, load the coding-frameworks skill (the UMPIRE method, the pattern taxonomy, the Big-O cheatsheet, Python idioms). It grounds every walkthrough below and is never read aloud verbatim.

Step 3 — Teach in chat

Explain entirely in chat — this is teach-first, not a graded run. Do not run any code in this command. You MAY offer to seed a scratch stub the user can try (e.g. point them at /practice-coding <id>), but explain runs nothing itself.