docs: Campaign LA — pinned launch-contract schema COMMITTED into plan LA1

The LA3 Opus review process note was right: the contract both sides
implement lived only in orchestrator prompts, which is exactly the drift
mode the pin exists to prevent (and it produced the paths-key CRITICAL).
The schema, field rules, probe-mode discriminator, and status vocabulary
are now a binding plan section; amendments change this text first,
implementations second. Ledger: LA3 fix round dispatched.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

tests/AcDream.App.Tests/Configuration/SessionConfigurationSharedFixtureTests.cs

@@ -0,0 +1,225 @@
+using System.Runtime.CompilerServices;
+using AcDream.App.Configuration;
+
+namespace AcDream.App.Tests.Configuration;
+
+/// <summary>
+/// Campaign LA slice LA1: proves the App config reader accepts the EXACT
+/// document the Headless reader also accepts —
+/// <c>tests/Fixtures/campaign-la/session-config-shared-fixture.json</c> is
+/// parsed by both <see cref="SessionConfigurationLoader"/> here and
+/// <c>AcDream.Headless.Configuration.HeadlessConfigurationLoader</c> in
+/// <c>AcDream.Headless.Tests</c>'s twin of this test. This is the
+/// pinned-contract acceptance test from
+/// <c>docs/plans/2026-08-14-launcher-campaign.md</c> LA1: "a SHARED fixture
+/// JSON parsed by both test suites proving the two readers accept the
+/// identical document." If either reader's DTO shape drifts from the pinned
+/// contract, ONE of these two tests fails.
+/// </summary>
+public sealed class SessionConfigurationSharedFixtureTests
+{
+    [Fact]
+    public void AppReaderAcceptsTheSharedFixtureAndParsesTheFiveNewFields()
+    {
+        (SessionConfiguration configuration, SessionDescriptor session) =
+            SessionConfigurationLoader.Load(SharedFixturePath());
+
+        Assert.Equal(1, configuration.Version);
+        Assert.Equal("shared-fixture", session.Id);
+        Assert.Equal("127.0.0.1", session.Endpoint.Host);
+        Assert.Equal(9000, session.Endpoint.Port);
+        Assert.Equal("sharedaccount", session.Account);
+        Assert.Equal("SharedToon", session.Character?.Name);
+        // App parses the policy field structurally but never consults it —
+        // the pinned contract's "parsed-and-ignored" clause.
+        Assert.Equal("idle", session.Policy?.Id);
+        Assert.Equal(
+            SessionCredentialProviderKind.Environment,
+            session.Credential.Provider);
+        Assert.Equal("SHARED_FIXTURE_PASSWORD", session.Credential.Reference);
+
+        Assert.Equal(["ExamplePlugin", "AnotherPlugin"], session.Plugins);
+        Assert.Equal(
+            ["/tell someone, hi", "/vt start"],
+            session.LoginCommands);
+        Assert.Equal(750, session.LoginCommandDelayMs);
+        Assert.Equal("shared-fixture-status.jsonl", session.StatusFile);
+    }
+
+    [Fact]
+    public void AbsentLaunchContractFieldsFallBackToPinnedDefaults()
+    {
+        using TemporaryFile file = TemporaryFile.Create(
+            """
+            {
+              "version": 1,
+              "sessions": [
+                {
+                  "id": "no-launch-contract-fields",
+                  "endpoint": { "host": "127.0.0.1", "port": 9000 },
+                  "account": "account",
+                  "credential": { "provider": "environment", "reference": "X" }
+                }
+              ]
+            }
+            """);
+
+        (_, SessionDescriptor session) = SessionConfigurationLoader.Load(file.Path);
+
+        Assert.Null(session.Character);
+        Assert.Null(session.Plugins);
+        Assert.Null(session.LoginCommands);
+        Assert.Equal(500, session.LoginCommandDelayMs);
+        Assert.Null(session.StatusFile);
+    }
+
+    [Fact]
+    public void MoreThanOneSessionFailsLoadForTheGraphicalHost()
+    {
+        using TemporaryFile file = TemporaryFile.Create(
+            """
+            {
+              "version": 1,
+              "sessions": [
+                {
+                  "id": "one",
+                  "endpoint": { "host": "127.0.0.1", "port": 9000 },
+                  "account": "account",
+                  "credential": { "provider": "environment", "reference": "A" }
+                },
+                {
+                  "id": "two",
+                  "endpoint": { "host": "127.0.0.1", "port": 9001 },
+                  "account": "account2",
+                  "credential": { "provider": "environment", "reference": "B" }
+                }
+              ]
+            }
+            """);
+
+        Assert.Throws<SessionConfigurationException>(
+            () => SessionConfigurationLoader.Load(file.Path));
+    }
+
+    [Fact]
+    public void EmptyPluginsEntryFailsLoad()
+    {
+        using TemporaryFile file = TemporaryFile.Create(
+            """
+            {
+              "version": 1,
+              "sessions": [
+                {
+                  "id": "bad-plugins",
+                  "endpoint": { "host": "127.0.0.1", "port": 9000 },
+                  "account": "account",
+                  "credential": { "provider": "environment", "reference": "X" },
+                  "plugins": ["Ok", "   "]
+                }
+              ]
+            }
+            """);
+
+        Assert.Throws<SessionConfigurationException>(
+            () => SessionConfigurationLoader.Load(file.Path));
+    }
+
+    [Fact]
+    public void NegativeLoginCommandDelayFailsLoad()
+    {
+        using TemporaryFile file = TemporaryFile.Create(
+            """
+            {
+              "version": 1,
+              "sessions": [
+                {
+                  "id": "bad-delay",
+                  "endpoint": { "host": "127.0.0.1", "port": 9000 },
+                  "account": "account",
+                  "credential": { "provider": "environment", "reference": "X" },
+                  "loginCommandDelayMs": -1
+                }
+              ]
+            }
+            """);
+
+        Assert.Throws<SessionConfigurationException>(
+            () => SessionConfigurationLoader.Load(file.Path));
+    }
+
+    [Fact]
+    public void BlankStatusFileFailsLoad()
+    {
+        using TemporaryFile file = TemporaryFile.Create(
+            """
+            {
+              "version": 1,
+              "sessions": [
+                {
+                  "id": "bad-status-file",
+                  "endpoint": { "host": "127.0.0.1", "port": 9000 },
+                  "account": "account",
+                  "credential": { "provider": "environment", "reference": "X" },
+                  "statusFile": "   "
+                }
+              ]
+            }
+            """);
+
+        Assert.Throws<SessionConfigurationException>(
+            () => SessionConfigurationLoader.Load(file.Path));
+    }
+
+    internal static string SharedFixturePath(
+        [CallerFilePath] string sourcePath = "") =>
+        Path.Combine(
+            FindRepositoryRoot(sourcePath),
+            "tests",
+            "Fixtures",
+            "campaign-la",
+            "session-config-shared-fixture.json");
+
+    private static string FindRepositoryRoot(string sourcePath)
+    {
+        string[] starts =
+        {
+            Path.GetDirectoryName(sourcePath) ?? string.Empty,
+            Directory.GetCurrentDirectory(),
+            AppContext.BaseDirectory,
+        };
+        foreach (string start in starts)
+        {
+            if (string.IsNullOrEmpty(start))
+                continue;
+
+            DirectoryInfo? directory = new(start);
+            while (directory is not null)
+            {
+                if (File.Exists(Path.Combine(directory.FullName, "AcDream.slnx")))
+                    return directory.FullName;
+                directory = directory.Parent;
+            }
+        }
+
+        throw new DirectoryNotFoundException(
+            "Could not find AcDream.slnx above the working or output directory.");
+    }
+
+    private sealed class TemporaryFile : IDisposable
+    {
+        private TemporaryFile(string path) => Path = path;
+
+        internal string Path { get; }
+
+        internal static TemporaryFile Create(string json)
+        {
+            string path = System.IO.Path.Combine(
+                System.IO.Path.GetTempPath(),
+                $"acdream-app-la1-{Guid.NewGuid():N}.json");
+            File.WriteAllText(path, json);
+            return new TemporaryFile(path);
+        }
+
+        public void Dispose() => File.Delete(Path);
+    }
+}