Restructure src/ modules with consistent internal organization

Reorganize major src/ directories to follow a consistent pattern with
core/, menu/, submenu/, inputs/, logs/, layout/, feedback/ subdirectories.

Changes by module:

- stores/: Move 5 store files to stores/core/
- utils/: Create core/ (terminal, tools, etc.) and menu/ (progress-bar)
- api/: Create copilot/core/, copilot/auth/, ollama/core/
- providers/: Create core/, copilot/core/, copilot/auth/, ollama/core/, login/core/
- ui/: Create core/, banner/core/, banner/menu/, spinner/core/,
       input-editor/core/, components/core/, components/menu/
- tools/: Create core/ for registry.ts and types.ts
- tui-solid/: Reorganize components/ into menu/, submenu/, inputs/,
              logs/, modals/, panels/, layout/, feedback/
- commands/: Create core/ for runner.ts and handlers.ts
- services/: Create core/ for agent.ts, permissions.ts, session.ts,
             executor.ts, config.ts

All imports updated to use new paths. TypeScript compilation verified.

src/services/agent-stream.ts

@@ -20,9 +20,9 @@ import type {
   PartialToolCall,
   StreamCallbacks,
 } from "@/types/streaming";
-import { chatStream } from "@providers/chat";
+import { chatStream } from "@providers/core/chat";
 import { getTool, getToolsForApi, refreshMCPTools } from "@tools/index";
-import { initializePermissions } from "@services/permissions";
+import { initializePermissions } from "@services/core/permissions";
 import { MAX_ITERATIONS, MAX_CONSECUTIVE_ERRORS } from "@constants/agent";
 import { createStreamAccumulator } from "@/types/streaming";