Remove chapter-level POV character

Character assignment now lives on beats only, per batch-assign. Drops
Chapter.PovCharacterId (entity, contracts, service, agent/import/MCP
tools, web UI) and the backing column via migration.

src/Novelly.Mcp/Tools/ManuscriptTools.cs

@@ -32,7 +32,6 @@ public static class ManuscriptTools
         CancellationToken ct,
         [Description("Position in the manuscript, 1-based.")] int? number = null,
         [Description("The chapter's outline summary paragraph.")] string? summary = null,
-        [Description("Id of the point-of-view character.")] Guid? povCharacterId = null,
         [Description("Where and when the chapter takes place.")] string? setting = null,
         [Description("Planned, Outlined, Drafted, Revised or Final.")] string? status = null,
         [Description("Target length in words.")] int? targetWordCount = null,
@@ -43,7 +42,6 @@ public static class ManuscriptTools
             title,
             number,
             summary,
-            povCharacterId,
             setting,
             status = status ?? "Planned",
             targetWordCount,
@@ -52,7 +50,7 @@ public static class ManuscriptTools
         }, ct);
 
     [McpServerTool(Name = "update_chapter")]
-    [Description("Revise a chapter's title, number, summary, POV character, setting, notes, status "
+    [Description("Revise a chapter's title, number, summary, setting, notes, status "
                  + "or drafted prose. Use 'prose' to write or replace the chapter's draft text in "
                  + "markdown; the word count is recomputed automatically.")]
     public static Task<CallToolResult> UpdateChapter(
@@ -62,7 +60,6 @@ public static class ManuscriptTools
         [Description("New title.")] string? title = null,
         [Description("Position in the manuscript.")] int? number = null,
         [Description("The chapter's outline summary paragraph.")] string? summary = null,
-        [Description("Id of the point-of-view character.")] Guid? povCharacterId = null,
         [Description("Where and when the chapter takes place.")] string? setting = null,
         [Description("Anything else worth recording.")] string? notes = null,
         [Description("Planned, Outlined, Drafted, Revised or Final.")] string? status = null,
@@ -70,5 +67,5 @@ public static class ManuscriptTools
         [Description("The chapter's drafted text, in markdown.")] string? prose = null,
         [Description("Tags for cross-referencing. Replaces the existing tags.")] string[]? tags = null) =>
         api.PatchAsync($"/api/chapters/{chapterId}",
-            new { title, number, summary, povCharacterId, setting, notes, status, targetWordCount, prose, tags }, ct);
+            new { title, number, summary, setting, notes, status, targetWordCount, prose, tags }, ct);
 }