fix(fleet): read existing fleet from fleet_deckies, not State["deployment"] (BUG-2)

The web deploy collision-guard read the existing fleet from the DB
State["deployment"] key, while the UI/get_deckies() read decnet-state.json.
A fleet established via CLI/seed lands in neither path the guard consulted,
so existing_deckies was empty, the additive guard ran blind, and the
reconciler tore the running fleet down to the single submitted decky
(BUG-2: silent fleet wipe, HTTP 202, no warning).

Converge both reads on fleet_deckies — the engine-mirrored table written on
every deploy/teardown (CLI and web), which fleet/reconciler.py already
documents as the store the orchestrator, dashboard, and REST API see. Each
row's decky_config column is a full DeckyConfig dump, so it rehydrates
losslessly into the collision-guard input. The handler also commits the
intended fleet to fleet_deckies synchronously so rapid sequential deploys
read a current fleet and the dashboard observes the new shape immediately.

State["deployment"] is retained for now — the mutate handlers and the
mutator engine still coordinate through it; consolidating them is tracked
in development/ADR-001-FLEET-SOURCE-OF-TRUTH.md (open question 7).

Tests seed fleet_deckies directly (also modelling the CLI-seeded scenario)
rather than chaining real deploys through the skipped contract-test path.

decnet/web/db/sqlmodel_repo/__init__.py

@@ -12,7 +12,6 @@ backends.  Dialect-specific behavior lives in subclasses:
 """
 from __future__ import annotations
 
-import asyncio
 import json
 import os
 
@@ -23,7 +22,6 @@ from typing import Any, Optional, List, cast
 from sqlalchemy import select
 from sqlalchemy.ext.asyncio import AsyncEngine, AsyncSession, async_sessionmaker
 
-from decnet.config import load_state
 from decnet.env import DECNET_ADMIN_USER, DECNET_ADMIN_PASSWORD
 from decnet.web.auth import get_password_hash
 from decnet.web.db.repository import BaseRepository
@@ -172,8 +170,14 @@ class SQLModelRepository(
         return None
 
     async def get_deckies(self) -> List[dict]:
-        _state = await asyncio.to_thread(load_state)
-        return [_d.model_dump() for _d in _state[0].deckies] if _state else []
+        # The fleet inventory the UI/API sees is fleet_deckies — the
+        # engine-mirrored table written on EVERY deploy/teardown (CLI or web),
+        # per the source-of-truth model documented in fleet/reconciler.py.
+        # Each row's decky_config column is a full DeckyConfig.model_dump(
+        # mode="json"), so it rehydrates to the same shape load_state() used
+        # to return. See development/ADR-001-FLEET-SOURCE-OF-TRUTH.md.
+        rows = await self.list_fleet_deckies()
+        return [r["decky_config"] for r in rows if r.get("decky_config")]
 
     # --------------------------------------------------------------- users