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/utils/core/index.ts

@@ -0,0 +1,8 @@
+/**
+ * Utils Core - Core utility functions
+ */
+
+export * from "./terminal";
+export * from "./string-helpers";
+export * from "./tools";
+export * from "./ensure-directories";

src/utils/index.ts

@@ -0,0 +1,12 @@
+/**
+ * Utils Module - Utility functions
+ */
+
+export * from "./core";
+export * from "./menu";
+export * from "./diff";
+export * from "./syntax-highlight/detect";
+export * from "./syntax-highlight/highlight";
+export * from "./tui-app/input-utils";
+export * from "./tui-app/mode-utils";
+export * from "./tui-app/paste-utils";

src/utils/menu/index.ts

@@ -0,0 +1,5 @@
+/**
+ * Utils Menu - Menu-related utilities
+ */
+
+export * from "./progress-bar";