feat(webapi): add solution overview summary endpoint

Adds GET /api/roslyn/solution/overview/summary with json|text|yaml formats.
Parses getsolutionoverview payload and renders compact summary for agents.

RoslynBridge.WebApi/Controllers/RoslynController.cs

@@ -1,5 +1,8 @@
 using Microsoft.AspNetCore.Mvc;
 using RoslynBridge.WebApi.Models;
+using System.Text;
+using System.Text.Json;
+using System.Linq;
 using RoslynBridge.WebApi.Services;
 
 namespace RoslynBridge.WebApi.Controllers;
@@ -91,6 +94,130 @@ public class RoslynController : ControllerBase
         return Ok(result);
     }
 
+    /// <summary>
+    /// Get a compact summary of the solution overview
+    /// </summary>
+    /// <param name="topNProjects">How many projects to list (by file count)</param>
+    /// <param name="includeNamespaces">Include top-level namespaces in summary</param>
+    /// <param name="format">One of: json | text | yaml</param>
+    /// <param name="instancePort">Optional: specific VS instance port to target</param>
+    /// <param name="cancellationToken">Cancellation token</param>
+    /// <returns>Compact summary as JSON or plain text</returns>
+    [HttpGet("solution/overview/summary")]
+    [ProducesResponseType(typeof(RoslynQueryResponse), StatusCodes.Status200OK)]
+    public async Task<IActionResult> GetSolutionOverviewSummary(
+        [FromQuery] int topNProjects = 5,
+        [FromQuery] bool includeNamespaces = true,
+        [FromQuery] string? format = "json",
+        [FromQuery] int? instancePort = null,
+        CancellationToken cancellationToken = default)
+    {
+        var request = new RoslynQueryRequest { QueryType = "getsolutionoverview" };
+        var result = await _bridgeClient.ExecuteQueryAsync(request, instancePort, cancellationToken);
+
+        if (!result.Success)
+        {
+            if (string.Equals(format, "json", StringComparison.OrdinalIgnoreCase))
+            {
+                return Ok(result);
+            }
+            var err = result.Error ?? "Unknown error";
+            return Content($"error: {err}", "text/plain", Encoding.UTF8);
+        }
+
+        // Expect Data as JsonElement; shape per Models.SolutionOverview
+        int projectCount = 0;
+        int documentCount = 0;
+        var projectsSummary = new List<(string Name, int FileCount)>();
+        var topLevelNamespaces = new List<string>();
+
+        if (result.Data is JsonElement dataEl && dataEl.ValueKind == JsonValueKind.Object)
+        {
+            if (dataEl.TryGetProperty("projectCount", out var pc)) projectCount = pc.GetInt32();
+            if (dataEl.TryGetProperty("documentCount", out var dc)) documentCount = dc.GetInt32();
+            if (includeNamespaces && dataEl.TryGetProperty("topLevelNamespaces", out var nsEl) && nsEl.ValueKind == JsonValueKind.Array)
+            {
+                foreach (var ns in nsEl.EnumerateArray())
+                {
+                    if (ns.ValueKind == JsonValueKind.String)
+                    {
+                        topLevelNamespaces.Add(ns.GetString() ?? string.Empty);
+                    }
+                }
+            }
+            if (dataEl.TryGetProperty("projects", out var prEl) && prEl.ValueKind == JsonValueKind.Array)
+            {
+                foreach (var p in prEl.EnumerateArray())
+                {
+                    string name = p.TryGetProperty("name", out var nEl) && nEl.ValueKind == JsonValueKind.String ? (nEl.GetString() ?? string.Empty) : string.Empty;
+                    int files = p.TryGetProperty("fileCount", out var fEl) && fEl.ValueKind == JsonValueKind.Number ? fEl.GetInt32() : 0;
+                    projectsSummary.Add((name, files));
+                }
+            }
+        }
+
+        var topProjects = projectsSummary
+            .OrderByDescending(p => p.FileCount)
+            .ThenBy(p => p.Name)
+            .Take(Math.Max(0, topNProjects))
+            .ToList();
+
+        if (string.Equals(format, "json", StringComparison.OrdinalIgnoreCase))
+        {
+            var compact = new
+            {
+                projectCount,
+                documentCount,
+                projects = topProjects.Select(p => new { name = p.Name, files = p.FileCount }).ToList(),
+                topLevelNamespaces = includeNamespaces ? topLevelNamespaces : null
+            };
+
+            return Ok(new RoslynQueryResponse
+            {
+                Success = true,
+                Message = "Compact solution overview",
+                Data = compact,
+                Error = null
+            });
+        }
+
+        // text or yaml: render a compact string
+        var sb = new StringBuilder();
+        if (string.Equals(format, "yaml", StringComparison.OrdinalIgnoreCase))
+        {
+            sb.AppendLine($"projectCount: {projectCount}");
+            sb.AppendLine($"documentCount: {documentCount}");
+            if (includeNamespaces)
+            {
+                sb.Append("topLevelNamespaces: [");
+                sb.Append(string.Join(", ", topLevelNamespaces));
+                sb.AppendLine("]");
+            }
+            sb.AppendLine("projects:");
+            foreach (var p in topProjects)
+            {
+                sb.AppendLine($"  - name: {p.Name}");
+                sb.AppendLine($"    files: {p.FileCount}");
+            }
+        }
+        else
+        {
+            // text
+            sb.AppendLine($"Projects: {projectCount} | Documents: {documentCount}");
+            if (includeNamespaces && topLevelNamespaces.Count > 0)
+            {
+                sb.AppendLine($"TopNamespaces: {string.Join(", ", topLevelNamespaces)}");
+            }
+            sb.AppendLine("Top Projects:");
+            foreach (var p in topProjects)
+            {
+                sb.AppendLine($" - {p.Name} ({p.FileCount})");
+            }
+        }
+
+        return Content(sb.ToString(), "text/plain", Encoding.UTF8);
+    }
+
     /// <summary>
     /// Get diagnostics (errors and warnings)
     /// </summary>