v10.22.0 embed-text excludes Nyx bookkeeping tags; coherence stays green

Fixed

• prep_memory_text folded ALL tags into the canonical embed-text, but Nyx
  rewrites bookkeeping tags (consolidated, nyx-split, merged-into-,
  split-from-, split-part-*) on every consolidation cycle. Because the
  coherence hash is computed over the embed-text, every memory that had
  ever been consolidated reported as content/vector mismatched (observed:
  723/723 on the production store) and doctor recommended a full
  re-embed that would just recur on the next Nyx run. The embed-text now
  excludes those churning, retrieval-irrelevant tags via stable_tags(),
  so coherence stays green across consolidation; semantic tags are kept.
  Adopting it requires a one-time re-embed of the active set (done on
  Epsilon: 723 verified, stale=0). 260 tests pass unchanged.