feat(ui): Rich tool result rendering with auto-detection and custom renderers

[mmogr]

Summary

Tool call results in the chat UI are displayed as raw JSON data. There are no tool-specific renderers that format results for human readability. For example, a web search tool might return a JSON array of results, but the user sees [{"title":"...","url":"...","snippet":"..."},...] instead of a formatted list with clickable links.

Current State

Tool call parts in messages have this structure (from types.ts):

// In GglibContent (assistant-ui parts):
{
  type: 'tool-call',
  toolCallId: string,
  toolName: string,
  args: Record<string, unknown>,
  argsText: string,
  result?: unknown,      // Raw JSON — rendered as-is
  isError?: boolean,
}

The rendering is generic — args and results are stringified JSON.

Proposed Solution

Phase 1: Tool result renderer extension point

Add a resultRenderer field to RegisteredTool:

export type ToolResultRenderer = (result: unknown, args: Record<string, unknown>) => {
  /** Summary text (always shown) */
  summary: string;
  /** Formatted detail (shown on expand, supports markdown) */
  detail?: string;
  /** Whether to show as collapsible (default: true for large results) */
  collapsible?: boolean;
};

export interface RegisteredTool {
  definition: ToolDefinition;
  executor: ToolExecutor;
  source: ToolSource;
  resultRenderer?: ToolResultRenderer;  // NEW
}

Phase 2: Default renderers for common patterns

Create sensible default renderers that auto-detect common result shapes:

Result Shape	Rendering
string	Inline text or markdown
{ error: string }	Red error badge with message
Array of objects	Table or formatted list
{ url: string, title: string }	Clickable link
Large JSON (>500 chars)	Collapsible with summary
{ content: string, ... }	Rendered content with metadata badge

Phase 3: MCP tool renderers

MCP tools can provide hints via their JSON Schema descriptions. Use these to infer rendering:

• If result has url fields → render as links
• If result is a list → render as numbered list
• If schema describes markdown or text content → render as formatted text

Files to Modify/Create

File	Change
src/services/tools/types.ts	Add ToolResultRenderer type, resultRenderer field
src/services/tools/registry.ts	Support resultRenderer in registration
src/services/tools/renderers/	New directory for default renderers
src/services/tools/renderers/defaultRenderer.ts	Auto-detection renderer
src/services/tools/renderers/index.ts	Barrel exports
src/components/	Update tool call display component to use renderers

Acceptance Criteria

• RegisteredTool supports optional resultRenderer field
• Default renderer auto-detects common result patterns (string, array, error, URL)
• Large results are collapsible with a visible summary
• Error results display distinctly (red styling, error icon)
• Built-in tools can register custom renderers
• MCP tools use the default renderer (with future extensibility for schema-driven rendering)
• Renderer output supports markdown formatting
• No regression — tools without renderers display as before (JSON fallback)