feat(config): add ConfigResolver with CLI>file>default precedence

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/ClaudeMailbox/Config/ConfigResolver.cs

@@ -0,0 +1,30 @@
+using ClaudeMailbox.Cli;
+
+namespace ClaudeMailbox.Config;
+
+public static class ConfigResolver
+{
+    public static DaemonConfig Build(string[] serveArgs, FileConfig file)
+    {
+        var cliPort = ParseIntOption(serveArgs, "--port");
+        var cliBind = ClientCommands.GetOption(serveArgs, "--bind");
+        var cliDbPath = ClientCommands.GetOption(serveArgs, "--db-path");
+
+        var port = cliPort ?? file.Port ?? DaemonConfig.DefaultPort;
+        var bind = cliBind ?? file.Bind ?? DaemonConfig.DefaultBindAddress;
+        var dbPathRaw = cliDbPath ?? file.DbPath ?? Paths.DefaultDbPath();
+
+        return new DaemonConfig
+        {
+            Port = port,
+            BindAddress = bind,
+            DbPath = Paths.Expand(dbPathRaw),
+        };
+    }
+
+    private static int? ParseIntOption(string[] args, string name)
+    {
+        var raw = ClientCommands.GetOption(args, name);
+        return int.TryParse(raw, out var v) ? v : null;
+    }
+}

tests/ClaudeMailbox.Tests/Config/ConfigResolverTests.cs

@@ -0,0 +1,59 @@
+using ClaudeMailbox.Config;
+
+namespace ClaudeMailbox.Tests.Config;
+
+public sealed class ConfigResolverTests
+{
+    [Fact]
+    public void CliFlag_WinsOverFile()
+    {
+        var file = new FileConfig { Port = 1000 };
+        var cfg = ConfigResolver.Build(new[] { "--port", "9999" }, file);
+        Assert.Equal(9999, cfg.Port);
+    }
+
+    [Fact]
+    public void File_WinsOverDefault()
+    {
+        var file = new FileConfig { Port = 1000, Bind = "0.0.0.0", DbPath = "/tmp/x.db" };
+        var cfg = ConfigResolver.Build(Array.Empty<string>(), file);
+        Assert.Equal(1000, cfg.Port);
+        Assert.Equal("0.0.0.0", cfg.BindAddress);
+        Assert.Equal(Paths.Expand("/tmp/x.db"), cfg.DbPath);
+    }
+
+    [Fact]
+    public void Default_UsedWhenNeitherCliNorFile()
+    {
+        var cfg = ConfigResolver.Build(Array.Empty<string>(), new FileConfig());
+        Assert.Equal(DaemonConfig.DefaultPort, cfg.Port);
+        Assert.Equal(DaemonConfig.DefaultBindAddress, cfg.BindAddress);
+        Assert.Equal(Paths.DefaultDbPath(), cfg.DbPath);
+    }
+
+    [Fact]
+    public void Mixed_CliPort_FileDbPath_DefaultBind()
+    {
+        var file = new FileConfig { DbPath = "/tmp/mixed.db" };
+        var cfg = ConfigResolver.Build(new[] { "--port", "7000" }, file);
+        Assert.Equal(7000, cfg.Port);
+        Assert.Equal(DaemonConfig.DefaultBindAddress, cfg.BindAddress);
+        Assert.Equal(Paths.Expand("/tmp/mixed.db"), cfg.DbPath);
+    }
+
+    [Fact]
+    public void CliDbPath_ExpandsEnvVars()
+    {
+        var file = new FileConfig();
+        var cfg = ConfigResolver.Build(new[] { "--db-path", "~/foo.db" }, file);
+        Assert.DoesNotContain("~", cfg.DbPath);
+    }
+
+    [Fact]
+    public void InvalidPortFlag_FallsBackToFileOrDefault()
+    {
+        var file = new FileConfig { Port = 4242 };
+        var cfg = ConfigResolver.Build(new[] { "--port", "not-a-number" }, file);
+        Assert.Equal(4242, cfg.Port);
+    }
+}