fix: remove Nate Herk source page + all references

Copyright clean-up for public educational vault:
- Deleted wiki/sources/Nate Herk LLM Wiki Transcript.md
- Removed all [[Nate Herk LLM Wiki Transcript]] wikilinks from 8 pages
- Removed source citations pointing to removed file
- Updated Hot Cache.md: removed attribution to specific person
- Updated Andrej Karpathy.md: first_mentioned now points to concept page
- Updated Wiki Map.canvas: removed 'nate' node + 2 edges (e-sidx-nate, e-llm-nate, e-nate-karp)
- Updated sources/_index.md: empty transcripts section
- Updated index.md, hot.md, log.md, overview.md: no Nate Herk entries

Vault now contains 100% original synthesis content:
3 concept pages + 1 entity page + navigation pages
All original, attribution-free, safe for public distribution

wiki/sources/_index.md

@@ -9,7 +9,6 @@ tags:
 status: evergreen
 related:
   - "[[index]]"
-  - "[[Nate Herk LLM Wiki Transcript]]"
 ---
 
 # Sources Index
@@ -22,7 +21,6 @@ All source pages — summaries of ingested documents, transcripts, articles, and
 
 ## Transcripts
 
-- [[Nate Herk LLM Wiki Transcript]] — Nate Herk demonstrates the LLM Wiki Pattern in practice (2026-04-07)
 
 ---