fix: repair mix test by removing forced MIX_ENV=dev and silencing test noise

- nix/shell.nix: remove export MIX_ENV=dev — it overrode Mix's automatic
  env selection, causing mix test to load dev config with no sandbox pool
- config/runtime.exs: use Ecto.Adapters.SQL.Sandbox pool (not
  DBConnection.Ownership) for test env — test_helper.exs uses the
  Sandbox API which requires the sandbox pool type
- test/test_helper.exs: silence NarrFetchWorker and ObanErrorReporter
  log noise at :critical level — expected error-path output when inline
  Oban jobs hit stubbed HTTP 500s

config/runtime.exs

@@ -13,7 +13,7 @@ require Logger
 if config_env() == :test do
   for repo <- [Microwaveprop.Repo] do
     existing = Application.get_env(:microwaveprop, repo, [])
-    Application.put_env(:microwaveprop, repo, Keyword.put(existing, :pool, DBConnection.Ownership))
+    Application.put_env(:microwaveprop, repo, Keyword.put(existing, :pool, Ecto.Adapters.SQL.Sandbox))
   end
 end
 

nix/shell.nix

@@ -229,8 +229,8 @@ mkShell {
     export SECRET_KEY_BASE="dev_secret_key_base_at_least_64_bytes_long_for_phoenix_to_accept_it_safely"
     export RELEASE_COOKIE="dev_release_cookie_for_distributed_erlang"
 
-    # Development environment
-    export MIX_ENV=dev
+    # Mix defaults to :dev for most tasks and :test for mix test;
+    # don't force MIX_ENV — let Mix select automatically.
     export PHX_HOST=localhost
     export PORT=4000
 

test/test_helper.exs

@@ -67,6 +67,15 @@ Logger.put_module_level(
   :critical
 )
 
+# Silence expected error-path noise during tests. Background workers
+# (NarrFetch, etc.) run inline under `testing: :inline` and hit stubbed
+# HTTP 500 responses — the warnings and Oban job-exception logs are
+# deliberate test behaviour, not bugs.
+Logger.put_module_level(
+  [Microwaveprop.Workers.NarrFetchWorker, Microwaveprop.ObanErrorReporter],
+  :critical
+)
+
 if Code.ensure_loaded?(Mox) do
   Mox.defmock(Microwaveprop.Valkey.MockAdapter, for: Microwaveprop.Valkey.Adapter)
 end