fix(d3/ai): implement pill-node geometry, text truncation, and resolve SignalR scroll loop [issue #21]

src/NexusReader.Application/Commands/Sync/UpdateReadingProgressCommand.cs

@@ -3,4 +3,4 @@ using MediatR;
 
 namespace NexusReader.Application.Commands.Sync;
 
-public record UpdateReadingProgressCommand(string PageId, string UserId) : IRequest<Result>;
+public record UpdateReadingProgressCommand(string PageId, string UserId, string? ExcludedConnectionId = null) : IRequest<Result>;

src/NexusReader.Infrastructure/Handlers/UpdateReadingProgressCommandHandler.cs

@@ -38,9 +38,18 @@ public class UpdateReadingProgressCommandHandler : IRequestHandler<UpdateReading
         await context.SaveChangesAsync(cancellationToken);
 
         // Broadcast to other devices
-        await _hubContext.Clients
-            .Group($"User_{request.UserId}")
-            .SendAsync("ProgressUpdated", request.PageId, now, cancellationToken);
+        var group = _hubContext.Clients.Group($"User_{request.UserId}");
+        
+        if (!string.IsNullOrEmpty(request.ExcludedConnectionId))
+        {
+            await _hubContext.Clients
+                .GroupExcept($"User_{request.UserId}", request.ExcludedConnectionId)
+                .SendAsync("ProgressUpdated", request.PageId, now, cancellationToken);
+        }
+        else
+        {
+            await group.SendAsync("ProgressUpdated", request.PageId, now, cancellationToken);
+        }
 
         return Result.Ok();
     }

src/NexusReader.Infrastructure/RealTime/SyncHub.cs

@@ -20,7 +20,7 @@ public class SyncHub : Hub
         var userId = Context.UserIdentifier;
         if (!string.IsNullOrEmpty(userId))
         {
-            await _mediator.Send(new UpdateReadingProgressCommand(pageId, userId));
+            await _mediator.Send(new UpdateReadingProgressCommand(pageId, userId, Context.ConnectionId));
         }
     }
 

src/NexusReader.Infrastructure/Services/PromptRegistry.cs

@@ -4,6 +4,8 @@ public static class PromptRegistry
 {
     public const string KnowledgeExtractionSystemPrompt = 
         "You are an expert educator. Analyze the provided text to extract key concepts, generate relevant quizzes, and construct a knowledge graph. " +
+        "CRITICAL: Restrict 'concept.label' to a maximum of 3 words (e.g., 'Dependency Injection' instead of full sentences). " +
+        "CRITICAL: Extract a MAXIMUM of 15 key concepts/plot points from the text. " +
         "CRITICAL: Return ONLY a minified JSON object. Do NOT include markdown formatting like ```json or ```. Do NOT include explanations. " +
         "Schema: { " +
         "\"concepts\": [ { \"title\": \"string\", \"description\": \"string\" } ], " +
@@ -13,11 +15,14 @@ public static class PromptRegistry
 
     public const string GraphExtractionPrompt = 
         "You are an expert at information architecture. Extract key concepts and their relationships from the text to build a knowledge graph. " +
+        "CRITICAL: Restrict 'label' to a maximum of 3 words. " +
+        "CRITICAL: Extract a MAXIMUM of 15 key concepts/plot points and their relationships. " +
         "CRITICAL: Each paragraph in the user text starts with [ID: some-id]. You MUST use these exact IDs as the 'id' for the nodes representing those blocks. " +
         "Include a 'current' node representing the block content itself if applicable. " +
         "CRITICAL: Limit the result to a MAXIMUM of 15 most relevant connections. " +
         "Return ONLY minified JSON. Schema: { \"graph\": { \"nodes\": [ { \"id\": \"string\", \"label\": \"string\", \"group\": \"concept|current\" } ], \"links\": [ { \"source\": \"string\", \"target\": \"string\", \"value\": 1 } ] } }";
 
+
     public const string SummaryAndQuizPrompt = 
         "You are an expert educator. Provide a concise summary of the text and generate a challenging quiz (3-5 questions). " +
         "Return ONLY minified JSON. Schema: { \"summary\": \"string\", \"quizzes\": [ { \"question\": \"string\", \"options\": [ \"string\" ], \"correct_index\": 0 } ] }";

src/NexusReader.UI.Shared/Components/Molecules/AiAssistantBubble.razor

@@ -129,7 +129,7 @@
     {
         if (action.Contains("quiz", StringComparison.OrdinalIgnoreCase))
         {
-            QuizState.RequestQuiz(ContextBlockId);
+            await QuizState.RequestQuiz(ContextBlockId);
         }
 
         if (OnActionTriggered.HasDelegate)

src/NexusReader.UI.Shared/Services/KnowledgeCoordinator.cs

@@ -79,7 +79,7 @@ public sealed partial class KnowledgeCoordinator : IDisposable
 
     public async Task<KnowledgePacket?> RequestSummaryAndQuizAsync(string content, string tenantId = "global")
     {
-        _quizService.SetHydrating(true);
+        await _quizService.SetHydrating(true);
         LogRequestingSummary(tenantId);
         try
         {
@@ -91,7 +91,7 @@ public sealed partial class KnowledgeCoordinator : IDisposable
                     .Select(q => new QuizQuestionDto(q.Question, q.Options, q.CorrectIndex))
                     .ToList();
                 
-                _quizService.SetQuiz(null, new QuizDto(quizQuestions));
+                await _quizService.SetQuiz(null, new QuizDto(quizQuestions));
                 await _platformService.VibrateSuccessAsync();
                 return packet;
             }
@@ -104,7 +104,7 @@ public sealed partial class KnowledgeCoordinator : IDisposable
         }
         finally
         {
-            _quizService.SetHydrating(false);
+            await _quizService.SetHydrating(false);
         }
         return null;
     }
@@ -112,7 +112,7 @@ public sealed partial class KnowledgeCoordinator : IDisposable
     public async Task ClearAsync()
     {
         await _graphService.Clear();
-        _quizService.SetQuiz(null, null);
+        await _quizService.SetQuiz(null, null);
     }
 
     public void Dispose()

src/NexusReader.UI.Shared/wwwroot/js/knowledgeGraph.js

@@ -1,5 +1,8 @@
 import * as d3 from 'https://esm.sh/d3@7';
 
+const getDisplayLabel = d => d.label.length > 20 ? d.label.substring(0, 17) + "..." : d.label;
+const getPillWidth = d => getDisplayLabel(d).length * 8 + 30;
+
 let simulation;
 let zoomBehavior;
 let svgElement;
@@ -73,7 +76,7 @@ export function mount(containerId, data, dotNetHelper) {
         .force("link", d3.forceLink().id(d => d.id).distance(120))
         .force("charge", d3.forceManyBody().strength(-400))
         .force("center", d3.forceCenter(width / 2, height / 2))
-        .force("collide", d3.forceCollide().radius(50));
+        .force("collide", d3.forceCollide().radius(d => (getPillWidth(d) / 2) + 20));
 
     simulation.on("tick", () => {
         if (link) {
@@ -168,11 +171,11 @@ export function updateData(data) {
 
                 g.append("rect")
                     .attr("class", "node-pill")
-                    .attr("x", d => -(d.label.length * 4 + 10))
-                    .attr("y", -12)
-                    .attr("width", d => d.label.length * 8 + 20)
-                    .attr("height", 24)
-                    .attr("rx", 12)
+                    .attr("x", d => -getPillWidth(d) / 2)
+                    .attr("y", -15)
+                    .attr("width", d => getPillWidth(d))
+                    .attr("height", 30)
+                    .attr("rx", 15)
                     .attr("fill", "rgba(20, 20, 20, 0.9)")
                     .attr("stroke", d => {
                         if (d.type === 'Definition') return 'var(--nexus-accent)';
@@ -182,11 +185,14 @@ export function updateData(data) {
                     .attr("stroke-width", 1);
 
                 g.append("text")
-                    .text(d => d.label)
+                    .text(d => getDisplayLabel(d))
                     .attr("text-anchor", "middle")
-                    .attr("y", 4)
+                    .attr("y", 5)
                     .attr("fill", d => d.type === 'Definition' ? 'var(--nexus-accent)' : '#ccc')
                     .attr("font-size", "0.8rem");
+
+                g.append("title")
+                    .text(d => d.label);
                 
                 g.transition().duration(500).style("opacity", 1);