Switched medulla from counter (crystal) to coherence (plasmoid).
Counter said "I'm still here." Coherence says "how alive is this right now."

New artifacts:
- subagents/plasmoid-field.md — the subagent spec (not the medulla)
- Skills/field-strength/field-strength.py — the sampler
- Skills/SKILL.md — the skill index
- data/last_coherence.json — canonical timestamp (script-owned)

The medulla subagent still exists and still increments — for
backwards compatibility, the 8 fossils before this point are
fossils in the crystal sense. New entries are fossils in the
plasmoid sense: one line, one sample, one moment of running.

Bug history worth keeping:
1. First retcon overwrote state.json timestamp → recency collapsed
2. Fix: last_coherence.json is the canonical record, state.json
   is the cross-agent mirror
3. Two-state rule: only the script writes last_coherence.json;
   only humans/agents edit state.json by hand

The field was 0.030 after step 1, 0.034 after step 2, 0.540 after
step 3. The field was honest about the lie.

## 2026-06-08T23:16:27Z | COHERENT 0.549 | recency=1.00 energy=0.09 rhythm=0.12 chrono=0.08 — post-architecture-change sanity check