Add character aliases/identity links, move-beats, keyboard help overlay

- Characters can carry aliases and be linked as the same underlying
  person (canonical SameCharacterAsId, optional reveal chapter/note),
  surfaced through the API, MCP tools, agent toolset, and web UI.
- Characters page redesigned as a filterable/sortable table (name+
  aliases, role, importance, occupation, tags) instead of a sidebar
  list, to stay usable as the cast grows.
- Beats can be moved between chapters (BeatService.MoveAsync + MCP/
  agent tool + endpoint).
- Add a keyboard-shortcuts help overlay (HelpButton/HelpOverlayContext)
  wired into the project layout.
- CLAUDE.md: require every frontend component to carry a unique id
  attribute; apply it to CharacterMultiSelect and MarkdownEditor.

src/Novelly.Mcp/Tools/CharacterTools.cs

@@ -48,7 +48,8 @@ public static class CharacterTools
         [Description("How they change over the course of the book.")] string? arcSummary = null,
         [Description("Speech patterns and register that make their dialogue theirs.")] string? voice = null,
         [Description("Anything else worth recording.")] string? notes = null,
-        [Description("Tags for cross-referencing. Unknown tags are created.")] string[]? tags = null) =>
+        [Description("Tags for cross-referencing. Unknown tags are created.")] string[]? tags = null,
+        [Description("Other names this character is known by.")] string[]? aliases = null) =>
         api.PostAsync($"/api/projects/{projectId}/characters", new
         {
             name,
@@ -67,7 +68,8 @@ public static class CharacterTools
             arcSummary,
             voice,
             notes,
-            tags
+            tags,
+            aliases
         }, ct);
 
     [McpServerTool(Name = "update_character")]
@@ -94,7 +96,8 @@ public static class CharacterTools
         [Description("How they change over the course of the book.")] string? arcSummary = null,
         [Description("Speech patterns and register.")] string? voice = null,
         [Description("Anything else worth recording.")] string? notes = null,
-        [Description("Tags for cross-referencing. Replaces the existing tags.")] string[]? tags = null) =>
+        [Description("Tags for cross-referencing. Replaces the existing tags.")] string[]? tags = null,
+        [Description("Other names this character is known by. Replaces the existing aliases.")] string[]? aliases = null) =>
         api.PatchAsync($"/api/characters/{characterId}", new
         {
             name,
@@ -113,7 +116,8 @@ public static class CharacterTools
             arcSummary,
             voice,
             notes,
-            tags
+            tags,
+            aliases
         }, ct);
 
     [McpServerTool(Name = "get_character_beats")]
@@ -191,4 +195,27 @@ public static class CharacterTools
         [Description("What the relationship is like, and where it is headed.")] string? description = null) =>
         api.PostAsync($"/api/characters/{characterId}/relationships",
             new { relatedCharacterId, relationshipType, description }, ct);
+
+    [McpServerTool(Name = "link_character_identity")]
+    [Description("Record that this character is really another character — e.g. a character introduced "
+                 + "under one name who is later revealed to be a character already in the project under "
+                 + "another name. Both characters keep their own dossier and beats; the canonical identity "
+                 + "is whichever character you link to.")]
+    public static Task<CallToolResult> LinkCharacterIdentity(
+        NovelApiClient api,
+        [Description("Id of the character being revealed as someone else.")] Guid characterId,
+        [Description("Id of the character this one really is.")] Guid sameCharacterAsId,
+        CancellationToken ct,
+        [Description("Id of the chapter where the reveal happens, if any.")] Guid? revealedInChapterId = null,
+        [Description("Context on the reveal, e.g. how and why the disguise held.")] string? note = null) =>
+        api.PutAsync($"/api/characters/{characterId}/identity",
+            new { sameCharacterAsId, revealedInChapterId, note }, ct);
+
+    [McpServerTool(Name = "unlink_character_identity")]
+    [Description("Remove a character's identity link, restoring it to its own separate identity.")]
+    public static Task<CallToolResult> UnlinkCharacterIdentity(
+        NovelApiClient api,
+        [Description("The character's id.")] Guid characterId,
+        CancellationToken ct) =>
+        api.DeleteAsync($"/api/characters/{characterId}/identity", ct);
 }