refactor: rename formatters to AgentFormatter/HumanFormatter for semantic clarity

ColorFormatter and MarkdownFormatter names obscured their actual purpose.
The formatters serve two distinct audiences: the AI agent (compressed,
token-efficient context) and the human (rich ANSI-colored terminal output).

- MarkdownFormatter → AgentFormatter (renderMarkdown* → renderAgent*)
- ColorFormatter → HumanFormatter (renderColor* → renderHuman*)
- useColors parameter → forHuman across the pipeline
- Import aliases Color/Markdown → Human/Agent
- API query param `colors=true` unchanged (backward compatible)

Pure rename refactor — no logic or behavior changes.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/services/worker/http/routes/SearchRoutes.ts

@@ -185,7 +185,7 @@ export class SearchRoutes extends BaseRouteHandler {
         session_id: 'preview-' + Date.now(),
         cwd: cwd
       },
-      true  // useColors=true for ANSI terminal output
+      true  // forHuman=true for ANSI terminal output
     );
 
     // Return as plain text
@@ -207,7 +207,7 @@ export class SearchRoutes extends BaseRouteHandler {
   private handleContextInject = this.wrapHandler(async (req: Request, res: Response): Promise<void> => {
     // Support both legacy `project` and new `projects` parameter
     const projectsParam = (req.query.projects as string) || (req.query.project as string);
-    const useColors = req.query.colors === 'true';
+    const forHuman = req.query.colors === 'true';
     const full = req.query.full === 'true';
 
     if (!projectsParam) {
@@ -238,7 +238,7 @@ export class SearchRoutes extends BaseRouteHandler {
         projects: projects,
         full
       },
-      useColors
+      forHuman
     );
 
     // Return as plain text