E4.3 bug: admin.go used mem["namespace"] which is empty (LanceDB
map keys are different from struct field names). Fixed by:
- Replace namespace lookup with content-based entity extraction
- Reuse distill/engine.go heuristic: capitalized words, Chinese
entities (2-20 chars), tech tokens (alphanumeric/digits)
- Get max graph degree across all extracted entities
- Add isStopWord, stripNonChinese, isTechToken, isAllDigits helpers
Fixes: degree always 0 in ShouldForget call, graph integration broken.
df2b648973