fix(worker): normalize model alias before preset lookup, wire DefaultMaxTurns as fallback

A full model id like claude-sonnet-4-6 in list_config.model never matched any
ModelPresets row (only bare aliases did), so every run under it landed on the
hardcoded 30-turn/DefaultLevel fallback instead of the sonnet preset row -
this is what killed two autonomous tasks at the 30-turn limit.

ModelRegistry.TryNormalizeAlias (non-throwing: exact match, then substring
match against a full model id) lets ModelPresets.For resolve a full model id
to its alias's preset row. For a model that still doesn't resolve, the
hardcoded 30 is replaced by a caller-supplied fallbackMaxTurns, and TaskRunner
now passes AppSettings.DefaultMaxTurns there - so that setting has a real
effect instead of being dead, matching the direction already noted in
docs/open.md.

tests/ClaudeDo.Data.Tests/ModelRegistryTests.cs

@@ -33,4 +33,28 @@ public class ModelRegistryTests
     {
         Assert.Equal(new[] { "haiku", "sonnet", "opus" }, ModelRegistry.ByCostAscending);
     }
+
+    [Theory]
+    [InlineData("sonnet", "sonnet")]
+    [InlineData("OPUS", "opus")]
+    [InlineData(" haiku ", "haiku")]
+    [InlineData("claude-sonnet-4-6", "sonnet")]
+    [InlineData("claude-opus-4-6", "opus")]
+    [InlineData("claude-haiku-4-5-20251001", "haiku")]
+    [InlineData("us.anthropic.claude-sonnet-4-6-v1:0", "sonnet")]
+    public void TryNormalizeAlias_matches_aliases_and_full_model_ids(string input, string expected)
+    {
+        Assert.Equal(expected, ModelRegistry.TryNormalizeAlias(input));
+    }
+
+    [Theory]
+    [InlineData(null)]
+    [InlineData("")]
+    [InlineData("   ")]
+    [InlineData("gpt-4")]
+    [InlineData("some-future-model")]
+    public void TryNormalizeAlias_never_throws_and_returns_null_when_unrecognized(string? input)
+    {
+        Assert.Null(ModelRegistry.TryNormalizeAlias(input));
+    }
 }