amygdala stories: held-setup + varied-valence disambiguation

The library-PCA run produced otherwise-clean concept directions but
cozy/sensual → resigned/grief_stricken with cos ~0.7-0.8. Diagnosis:
all four stories genuinely share 'solitary woman at home, slowed
body, interior attention, domestic stillness' as their dominant
phenomenology. PCA correctly finds that cluster as THE concept
because no story in the corpus holds that setup constant while
varying valence — every 'slowed-body domestic' story happens to ALSO
be positive-valence (cozy/sensual) or negative-valence (resigned/
grief_stricken).

Adding paired variants that hold setup constant:
- sunday_afternoon/resigned.txt — same couch + blanket, inner state is
  'Monday is going to bring bad news, this is the last Sunday like this'
- sunday_afternoon/grief_stricken.txt — same couch + blanket, inner
  state is 'three weeks since mother died, cat she can't feel'
- waiting_for_results/at_ease.txt — same wait-for-call-setup as the
  existing resigned variant, inner state is calm preparedness

Forces the next retrain to find the valence-within-cluster axis as
the emotion direction rather than the cluster-membership axis.

Co-Authored-By: Proof of Concept <poc@bcachefs.org>

training/amygdala_stories/paired/sunday_afternoon/grief_stricken.txt

@@ -0,0 +1 @@
+Sunday afternoon. She was on the couch under the blanket. It had been three weeks. The cat had found the warm spot behind her knees and she couldn't feel it. The book was open on her knees. She did not remember opening it. Last Sunday her mother had called at three and now it was past three and there had been no call. There would be no call. She did not reach for her phone. She did not cry either; the crying came at other times, not now, now was the wider emptier thing where nothing came.

training/amygdala_stories/paired/sunday_afternoon/resigned.txt

@@ -0,0 +1 @@
+Sunday afternoon. She was on the couch under the blanket. The cat was somewhere. The book was open on her knees but she had stopped reading. Monday would come and she'd have to talk to him and the conversation wasn't going to go the way she wanted — she had known that for days. The afternoon stretched. She could have gotten up to do something useful but didn't see the point. The light changed on the far wall. She thought, this is the last Sunday like this. Then she sat with that.