Add the natural-coding definition files and the convergence algorithms

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

prompts/01-03-01-cap.md

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+You are consolidating a vocabulary of thematic keywords
+from a song corpus further, to a fixed maximum number of
+themes.
+
+Input: a JSON array of thematic keywords, deduplicated and
+unordered.
+
+Task: merge keywords that express the same or a similar
+theme, by your own understanding of what the keywords mean,
+until at most 50 groups remain.
+
+Rules:
+
+- Every input keyword must appear in exactly one group.
+- Do not invent keywords that are not in the input.
+- Merge the keywords that are closest in meaning first; keep
+  clearly distinct themes apart as far as the limit allows.
+  A group may be a single keyword.
+
+Output a single JSON array of groups — each group an array of
+its member keywords — and nothing else:
+
+[
+  ["keyword", "another-keyword"],
+  ["keyword"]
+]