fix: persona_state SET body → canonical {pad:{pleasure,arousal,dominance}} + re-vendor Tier-3 prose (v0.19.7)

worldtree-dev landed the Tier-3 persona/memory/persona_state prose docs
(c9e59ec) — shapes that serialize as freeform Any in the OpenAPI, so the
prose markdown is their source of truth. Re-vendored docs/conversation-api-spec.md
(tolerate_drift markdown pin; worldtree-spec-rev 879cefe→c9e59ec).

Consumer alignment: --set-persona-pad / _set_persona_probe was building
{pad:[list]}, but the canonical POST /sessions/{id}/persona_state body (#317)
is {pad:{pleasure,arousal,dominance}} (named dict). Aligned the probe to the
named dict + a len!=3 guard; updated contract #2's note, the set_persona_state
docstring, and the tests. The set_persona_state wrapper was already correct
(freeform pass-through) — only the CLI probe's body construction drifted.

Suite 602 green. (Also this session: heid-code-review on the #347 slice
returned unanimous zero drift across all three panel arms.)

docs/contracts/issues/2.contract.md

@@ -322,7 +322,9 @@ via a `--characters` one-shot lifecycle probe; persona-state write surfaced via
 wrappers: parsed dict verbatim (or None on 204), any off-status → SessionApiFailed.
 **Note:** `set_persona_state`'s request body is FREEFORM — the frozen OpenAPI 2.2.0
 declares no request schema and the prose spec documents only the GET counterpart,
-so the caller supplies the snapshot shape (`--set-persona-pad` sends `{pad:[…]}`).
+so the caller supplies the snapshot shape. **Canonical (worldtree-dev prose #317,
+`c9e59ec`): `{pad:{pleasure,arousal,dominance}}` — a named-key dict, NOT a list;
+`--set-persona-pad` builds + sends the named dict (each float in [-1,1]).**
 
 ```contract
 FN list_character_models(client) -> dict[str, Any]
@@ -369,7 +371,7 @@ POST: [POST-001 return_value] on 204 returns None; [POST-002 side_effect] outbou
 STEPS:
   1. [sequential, prescriptive] resp = await client.post(f"/sessions/{session_id}/persona_state", json=snapshot); IF 204 RETURN None; ELSE RAISE SessionApiFailed
 TESTS:
-  happy [happy]: 204 → None; body == {"pad":[...]} verbatim
+  happy [happy]: 204 → None; body == {"pad":{"pleasure","arousal","dominance"}} verbatim (canonical named-key dict, #317)
   non_204 [error]: 422 → SessionApiFailed(422)
 ```