Replace chapter setting with multi-select locations; add chapter character summary

Chapters now carry many Locations (new Tags-style entity with cross-referencing)
instead of a single free-text Setting field, with a Locations tab on the novel
for browsing them and seeing every chapter set at each one. Also surfaces the
distinct characters appearing in a chapter's beats, linked, under the beat/word
count on the outline tab.

src/Novelly.Api/Agent/NovelAgentToolset.cs

@@ -3,6 +3,7 @@ using Novelly.Api.Beats;
 using Novelly.Api.Chapters;
 using Novelly.Api.Characters;
 using Novelly.Api.Common;
+using Novelly.Api.Locations;
 using Novelly.Api.Novels;
 using Novelly.Api.Questions;
 using Novelly.Api.Tags;
@@ -29,6 +30,7 @@ public class NovelAgentToolset(
     ChapterService chapters,
     BeatService beats,
     TagService tags,
+    LocationService locations,
     OpenQuestionService questions,
     ILogger<NovelAgentToolset> logger)
 {
@@ -366,6 +368,25 @@ public class NovelAgentToolset(
                 return await OrNotFound(tags.GetReferencesAsync(tagId, ct), t => t.ToReferencesResponse(), "Tag", tagId);
             });
 
+        yield return new AgentTool(
+            "list_locations",
+            "List the novel's locations with how many chapters are set there. "
+            + "Read this before inventing a new location so you reuse the writer's vocabulary.",
+            new JsonSchemaBuilder().Build(),
+            async (novelId, _, ct) => await locations.ListAsync(novelId, ct));
+
+        yield return new AgentTool(
+            "get_location_references",
+            "Cross-reference a location: every chapter set there.",
+            new JsonSchemaBuilder()
+                .Str("location_id", "Id of the location to trace.", required: true)
+                .Build(),
+            async (_, input, ct) =>
+            {
+                var locationId = JsonInput.RequiredGuid(input, "location_id");
+                return await OrNotFound(locations.GetReferencesAsync(locationId, ct), l => l.ToReferencesResponse(), "Location", locationId);
+            });
+
         yield return new AgentTool(
             "list_chapters",
             "List the novel's chapters in manuscript order with beat and word counts.",
@@ -391,7 +412,7 @@ public class NovelAgentToolset(
                 .Str("title", "Chapter title.", required: true)
                 .Int("number", "Position in the manuscript, 1-based.")
                 .Str("summary", "What the chapter covers.")
-                .Str("setting", "Where and when the chapter takes place.")
+                .StringArray("locations", "Where and when the chapter takes place. Unknown locations are created.")
                 .Str("notes", "Anything else worth recording.")
                 .Enum("status", "Drafting status.", System.Enum.GetNames<DraftStatus>())
                 .Int("target_word_count", "Target length in words.")
@@ -402,7 +423,7 @@ public class NovelAgentToolset(
                 JsonInput.RequiredString(input, "title"),
                 JsonInput.Int(input, "number"),
                 JsonInput.String(input, "summary"),
-                JsonInput.String(input, "setting"),
+                JsonInput.Strings(input, "locations"),
                 JsonInput.String(input, "notes"),
                 JsonInput.Enum<DraftStatus>(input, "status") ?? DraftStatus.Planned,
                 JsonInput.Int(input, "target_word_count"),
@@ -411,7 +432,7 @@ public class NovelAgentToolset(
 
         yield return new AgentTool(
             "update_chapter",
-            "Revise a chapter's title, number, summary, setting, notes, status or drafted "
+            "Revise a chapter's title, number, summary, locations, notes, status or drafted "
             + "prose. Use 'prose' to write or replace the chapter's draft text in markdown; the "
             + "word count is recomputed automatically.",
             new JsonSchemaBuilder()
@@ -419,7 +440,7 @@ public class NovelAgentToolset(
                 .Str("title", "New title.")
                 .Int("number", "Position in the manuscript.")
                 .Str("summary", "What the chapter covers.")
-                .Str("setting", "Where and when the chapter takes place.")
+                .StringArray("locations", "Where and when the chapter takes place. Replaces the existing locations. Unknown locations are created.")
                 .Str("notes", "Anything else worth recording.")
                 .Enum("status", "Drafting status.", System.Enum.GetNames<DraftStatus>())
                 .Int("target_word_count", "Target length in words.")
@@ -435,7 +456,7 @@ public class NovelAgentToolset(
                         JsonInput.String(input, "title"),
                         JsonInput.Int(input, "number"),
                         JsonInput.String(input, "summary"),
-                        JsonInput.String(input, "setting"),
+                        JsonInput.Strings(input, "locations"),
                         JsonInput.String(input, "notes"),
                         JsonInput.Enum<DraftStatus>(input, "status"),
                         JsonInput.Int(input, "target_word_count"),