feat(#20): persona + authored-history + first-message onto the wt adapter (slice-3)

Slice-3 of the worldtree-sdk cutover: migrate the session persona-state write,
the #347 authored-history write, and get_session_messages onto ratatoskr.wt, and
route the first-message preset seed through the adapter. Retire the last
hand-rolled sessions.py paths the --seed-first-message probe kept alive
(create_session + SessionInfo, set_persona_state, write_authored_history,
get_session_messages, _bifrost_error_from).

- wt.set_persona_state (SDK PadState) — the CLI passes three finite PAD axes; the
  SDK owns the {"pad": {...}} wire (#317). No route-specific error row → the
  SessionApiFailed default.
- wt.write_authored_history (SDK write_history) — v1 author=assistant; 404 →
  AuthoredHistoryUnavailable (hide-existence; the route is the discriminator,
  never the body); every other ApiError → the default. Drops the unused
  author/effects/claimed_original_at params (no caller uses them).
- first_message.seed_preset_first_message now takes a WorldtreeClient and routes
  through wt.write_authored_history; the best-effort invariants (INV-001..004,
  never-raise/never-block/one-write/zero-worldtree-source-import) are unchanged.
  Tests drive a fake WorldtreeClient — the wire is the SDK's to prove.
- CLI --set-persona-pad / --seed-first-message + the _amain and web create-path
  first-message seeds rewired onto the adapter. --set-persona-pad pre-validates
  PAD finiteness (clean usage_error, never a crash on the SDK ConfigurationError).

LIVE-SMOKE on personal :8081 (b128, INV-CUT-5): --seed-first-message → 201
(seq=0, phase=seeded) → read-back verbatim; --set-persona-pad → 204; the --new
create-path preset seed observed routing through the adapter. All slice-3 route
families proven end-to-end through the ratatoskr surface.

docs/coverage-map.md + first_message.contract.md re-anchored onto the adapter;
the slice-2 create/stream/cancel rows re-anchored too (they still named the
deleted sse_client/sessions symbols).

Suite 466 green; mypy no new errors (baseline 22 → 20 in the touched modules);
ruff clean. INV-CUT-1..5 held. Bifrost provider planes untouched.

docs/coverage-map.md

@@ -84,11 +84,11 @@ sub-gap).
 
 | Endpoint | Status | Where consumed | Note |
 |---|---|---|---|
-| `POST /sessions` | ✅ | `sessions.py` `create_session` → `cli.py`,`tui.py`,`web/server.py` | + `end_user_id`, `bifrost` binding; 404→AgentNotFound, 502→BifrostHandshakeFailed. **v0.21.2 (#19): ephemeral-template (Echo) create** — `config` passthrough (`--system-prompt`), `role` not `model` (W-4), `kind`/`config` captured; 422 ephemeral_requires_config now reachable-and-handled. Depth enhancement to an already-covered route — count unchanged |
-| `POST /sessions/{id}/messages` (turn stream, SSE) | ✅ | `sse_client.py:484` `stream_turn` → cli/tui/web | the primary surface; 409→AgentNotAvailable, 503→TurnLaunchUnavailable (b2 #331) |
-| `POST /sessions/{id}/history` (authored-history-write, #347) | ✅ | `sessions.py:583` `write_authored_history` → `cli.py:758` `--seed-first-message` | v1: author=assistant, effects=none, per-session idempotency; 404→AuthoredHistoryUnavailable (hide-existence: feature-absent, never probe); 409/422 mapped. **LIVE-PROVEN 2026-07-06** on personal :8081 (grant applied via a rule-based Heimdall allow, worldtree-dev): create mimir session → seed → **201** (seq=0, phase=seeded, turn_id=1798) → GET /messages reads it back as a plain role=assistant turn (model-invisible provenance confirmed). Hide-404 for ungranted is unit+probe covered |
-| `GET /sessions/{id}/messages` (history) | ✅ | `sessions.py:635` `get_session_messages` → `cli.py:758` `--seed-first-message` read-back | un-deferred as the #347 seed read-back — confirms model-invisible provenance (a seed reads back as a normal `role=assistant` turn) |
-| `POST /sessions/{id}/turns/{turn_id}/cancel` | ✅ | `sse_client.py:581` → cli/tui/web | two-stage Ctrl-C; 404/409 mapped |
+| `POST /sessions` | ✅ | `wt.py` `create_session` (SDK `sessions.create`) → `cli.py`,`web/server.py` | **wt-adapter re-anchored (slice-2, #20)** — + `end_user_id`, `bifrost` binding (consumer-key via SDK per-request auth), `config` passthrough; 404→AgentNotFound, bound-502→BifrostHandshakeFailed. Ephemeral-template (Echo) create (#19) carried through the adapter. Depth enhancement to an already-covered route — count unchanged |
+| `POST /sessions/{id}/messages` (turn stream, SSE) | ✅ | `wt.py` `stream_turn` (SDK resilient `sessions.stream_turn`, auto-resume) → cli/web | **wt-adapter re-anchored (slice-2, #20)** — the primary surface; 409→AgentNotAvailable, 503→TurnLaunchUnavailable, drop→SseConnectionDropped, protocol→same-named; absorbs the old `reconnect_turn` |
+| `POST /sessions/{id}/history` (authored-history-write, #347) | ✅ | `wt.py` `write_authored_history` (SDK `sessions.write_history`) → `cli.py` `--seed-first-message`, `first_message.py` `seed_preset_first_message` (create-path seed) | **wt-adapter re-anchored (slice-3, #20)** — SDK owns the entry shape; v1 author=assistant; 404→AuthoredHistoryUnavailable (hide-existence, route is the discriminator, never probe); 409/422→SessionApiFailed default. **LIVE-SMOKE 2026-07-19** on personal :8081 (b128): `--seed-first-message` on a sindra session → **201** (seq=0, phase=seeded, turn_id=2294) → read-back verbatim; create-path preset seed observed via `--new`. (Prior 2026-07-06 hand-rolled proof superseded.) |
+| `GET /sessions/{id}/messages` (history) | ✅ | `wt.py` `get_session_messages` (SDK `sessions.messages`) → `cli.py` `--seed-first-message` read-back, `web/server.py` messages proxy | **wt-adapter re-anchored (slice-3, #20)** — the #347 seed read-back; open-world passthrough. **LIVE-SMOKE 2026-07-19**: read-back rendered the seeded seq-0 turn as a plain role=assistant message (model-invisible provenance confirmed) |
+| `POST /sessions/{id}/turns/{turn_id}/cancel` | ✅ | `wt.py` `cancel_turn` (SDK `sessions.cancel_turn`) → cli/web | **wt-adapter re-anchored (slice-2, #20)** — two-stage Ctrl-C; 404→CancelTurnNotFound, 409→CancelAlreadyCompleted, late-cancel 200 (`cancelled=False`) is a benign result, not an error |
 | `GET /agents` | ✅ | `sessions.py:341` → `tui.py:1472`,`web/server.py:100` | Tier-1 roster; merged with local index |
 | `GET /agents/{id}/persona_state` | ✅ | `sessions.py:384` → `tui.py:1132`,`web/server.py:386` | persona hydrate; 404/403 mapped |
 | `POST /agents/define` | ✅ | `tier3.py:175` → `_run_define` | Tier-3 create |
@@ -103,7 +103,7 @@ sub-gap).
 | `POST /characters` | ✅ | `sessions.py` `create_character` → `cli.py` `--characters` | create transient character (#161) |
 | `GET /characters/{id}/state` | ✅ | `sessions.py` `get_character_state` → `cli.py` `--characters` | live character PAD/emotions (#161) |
 | `DELETE /characters/{id}` | ✅ | `sessions.py` `delete_character` → `cli.py` `--characters` | remove transient character (#161) |
-| `POST /sessions/{id}/persona_state` | ✅ | `sessions.py` `set_persona_state` → `cli.py` `--set-persona-pad` | persona-state write / affect injection (freeform body — unpinned in the frozen surface) |
+| `POST /sessions/{id}/persona_state` | ✅ | `wt.py` `set_persona_state` (SDK `sessions.set_persona_state`, `PadState`) → `cli.py` `--set-persona-pad` | **wt-adapter re-anchored (slice-3, #20)** — SDK owns the canonical `{"pad": {...}}` wire (#317); CLI passes the 3 PAD axes (finiteness pre-validated); 204→None, else SessionApiFailed default. **LIVE-SMOKE 2026-07-19** on personal :8081: `--set-persona-pad 0.4,0.1,-0.2` → **204** |
 
 **Sub-gaps inside ✅ path groups** (the method we use is live; a sibling method
 on the same path is an unwired frontier item — see frontier Tier 1):