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.Api/Agent/NovelAgentToolset.cs

@@ -151,7 +151,8 @@ public class NovelAgentToolset(
                 JsonInput.String(input, "arc_summary"),
                 JsonInput.String(input, "voice"),
                 JsonInput.String(input, "notes"),
-                JsonInput.Strings(input, "tags")), ct), c => c.ToResponse(), "Project", projectId));
+                JsonInput.Strings(input, "tags"),
+                JsonInput.Strings(input, "aliases")), ct), c => c.ToResponse(), "Project", projectId));
 
         yield return new AgentTool(
             "update_character",
@@ -181,7 +182,42 @@ public class NovelAgentToolset(
                         JsonInput.String(input, "arc_summary"),
                         JsonInput.String(input, "voice"),
                         JsonInput.String(input, "notes"),
-                        JsonInput.Strings(input, "tags")), ct), c => c.ToResponse(), "Character", characterId);
+                        JsonInput.Strings(input, "tags"),
+                        JsonInput.Strings(input, "aliases")), ct), c => c.ToResponse(), "Character", characterId);
+            });
+
+        yield return new AgentTool(
+            "link_character_identity",
+            "Record that a character is really another character — e.g. one introduced under one name "
+            + "who is later revealed to be a character already in the project under another name. Both "
+            + "keep their own dossier and beats; the canonical identity is whichever character you link to.",
+            new JsonSchemaBuilder()
+                .Str("character_id", "Id of the character being revealed as someone else.", required: true)
+                .Str("same_character_as_id", "Id of the character this one really is.", required: true)
+                .Str("revealed_in_chapter_id", "Id of the chapter where the reveal happens, if any.")
+                .Str("note", "Context on the reveal, e.g. how and why the disguise held.")
+                .Build(),
+            async (_, input, ct) =>
+            {
+                var characterId = JsonInput.RequiredGuid(input, "character_id");
+                return await OrNotFound(characters.LinkIdentityAsync(
+                    characterId,
+                    new LinkCharacterIdentityRequest(
+                        JsonInput.RequiredGuid(input, "same_character_as_id"),
+                        JsonInput.Guid(input, "revealed_in_chapter_id"),
+                        JsonInput.String(input, "note")), ct), c => c.ToResponse(), "Character", characterId);
+            });
+
+        yield return new AgentTool(
+            "unlink_character_identity",
+            "Remove a character's identity link, restoring it to its own separate identity.",
+            new JsonSchemaBuilder()
+                .Str("character_id", "Id of the character to unlink.", required: true)
+                .Build(),
+            async (_, input, ct) =>
+            {
+                var characterId = JsonInput.RequiredGuid(input, "character_id");
+                return await DeletedOrNotFound(characters.UnlinkIdentityAsync(characterId, ct), "Character", characterId);
             });
 
         yield return new AgentTool(
@@ -289,6 +325,27 @@ public class NovelAgentToolset(
                             .Where(g => g != Guid.Empty)]), ct), list => list.Select(b => b.ToResponse()), "Chapter", chapterId);
             });
 
+        yield return new AgentTool(
+            "move_beats",
+            "Move one or more beats from one chapter to another, appending them to the target "
+            + "chapter's end in the order given.",
+            new JsonSchemaBuilder()
+                .Str("chapter_id", "Id of the beats' current chapter.", required: true)
+                .Str("target_chapter_id", "Id of the chapter to move the beats into.", required: true)
+                .StringArray("beat_ids", "Ids of the beats to move.", required: true)
+                .Build(),
+            async (_, input, ct) =>
+            {
+                var chapterId = JsonInput.RequiredGuid(input, "chapter_id");
+                return await OrNotFound(beats.MoveAsync(
+                    chapterId,
+                    new MoveBeatsRequest(
+                        JsonInput.RequiredGuid(input, "target_chapter_id"),
+                        [.. (JsonInput.Strings(input, "beat_ids") ?? [])
+                            .Select(id => Guid.TryParse(id, out var g) ? g : Guid.Empty)
+                            .Where(g => g != Guid.Empty)]), ct), list => list.Select(b => b.ToResponse()), "Chapter", chapterId);
+            });
+
         yield return new AgentTool(
             "list_tags",
             "List the project's tags with how many characters, chapters and beats carry each. "
@@ -596,7 +653,8 @@ public class NovelAgentToolset(
             .Str("arc_summary", "How they change over the course of the book.")
             .Str("voice", "Speech patterns and register that make their dialogue theirs.")
             .Str("notes", "Anything else worth recording.")
-            .StringArray("tags", "Tags for cross-referencing. Replaces the existing tags.");
+            .StringArray("tags", "Tags for cross-referencing. Replaces the existing tags.")
+            .StringArray("aliases", "Other names this character is known by. Replaces the existing aliases.");
     }
 
     private static JsonSchemaBuilder BeatSchema() =>