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>

src/AcDream.Headless/Configuration/HeadlessConfiguration.cs

@@ -72,6 +72,38 @@ internal sealed record HeadlessSessionDescriptor
     /// legal no-ops.
     /// </summary>
     public Dictionary<string, bool>? CharacterOptions { get; init; }
+
+    /// <summary>
+    /// Campaign LA slice LA1: plugin ids to load from the standard plugins
+    /// directory (<c>docs/plans/2026-08-14-launcher-campaign.md</c> LA1).
+    /// Absent means load every discovered plugin (today's dev behavior);
+    /// LA5 wires this into an actual allow-list filter. Parsed and carried
+    /// here now so the session-config shape is stable before LA5 lands.
+    /// </summary>
+    public List<string>? Plugins { get; init; }
+
+    /// <summary>
+    /// Campaign LA slice LA1: ordered chat-typed strings run once the
+    /// session enters world. LA6 wires actual execution; parsed and carried
+    /// here now.
+    /// </summary>
+    public List<string>? LoginCommands { get; init; }
+
+    /// <summary>
+    /// Campaign LA slice LA1: inter-command delay for
+    /// <see cref="LoginCommands"/>, in milliseconds. Matches the pinned
+    /// launch-contract default (500 ms) when the field is absent from the
+    /// document.
+    /// </summary>
+    public int LoginCommandDelayMs { get; init; } = 500;
+
+    /// <summary>
+    /// Campaign LA slice LA1: absolute path for this session's status-event
+    /// JSONL stream (<c>docs/superpowers/specs/2026-08-14-launcher-campaign-design.md</c>
+    /// §6). Absent means no <see cref="AcDream.Runtime.Session.SessionStatusWriter"/>
+    /// is constructed for this session.
+    /// </summary>
+    public string? StatusFile { get; init; }
 }
 
 internal sealed class HeadlessEndpointDescriptor

src/AcDream.Headless/Configuration/HeadlessConfigurationLoader.cs

@@ -215,6 +215,42 @@ internal static class HeadlessConfigurationLoader
         }
 
         ValidateCharacterOptions(session);
+        ValidateLaunchContractFields(session);
+    }
+
+    /// <summary>
+    /// Campaign LA slice LA1: validates the four new optional per-session
+    /// fields shared with the App session-config reader (see
+    /// <c>docs/plans/2026-08-14-launcher-campaign.md</c> LA1's pinned
+    /// contract). All four stay optional; only their SHAPE is checked here
+    /// — parsing/executing <c>plugins</c>/<c>loginCommands</c> is LA5/LA6.
+    /// </summary>
+    private static void ValidateLaunchContractFields(HeadlessSessionDescriptor session)
+    {
+        if (session.Plugins is { } plugins)
+        {
+            foreach (string? plugin in plugins)
+            {
+                if (string.IsNullOrWhiteSpace(plugin))
+                {
+                    throw new HeadlessConfigurationException(
+                        $"Session '{session.Id}' plugins entries must be non-empty strings.");
+                }
+            }
+        }
+
+        if (session.LoginCommandDelayMs < 0)
+        {
+            throw new HeadlessConfigurationException(
+                $"Session '{session.Id}' loginCommandDelayMs must be non-negative.");
+        }
+
+        if (session.StatusFile is not null
+            && string.IsNullOrWhiteSpace(session.StatusFile))
+        {
+            throw new HeadlessConfigurationException(
+                $"Session '{session.Id}' statusFile must be a non-empty path when present.");
+        }
     }
 
     /// <summary>