refactor(build): migrated imports to path aliases with per-package tsconfig support

- converted relative imports to path aliases ($c/*, $ai/*, $tui/*, etc.) across all packages
- added per-package tsconfig.json with complete path mappings for runtime resolution
- set importModuleSpecifier to non-relative for IDE auto-import preferences
- updated dev script to run from monorepo root for consistent path resolution

packages/coding-agent/test/core/python-kernel-ws.test.ts

@@ -1,9 +1,5 @@
 import { describe, expect, it } from "bun:test";
-import {
-	deserializeWebSocketMessage,
-	type JupyterMessage,
-	serializeWebSocketMessage,
-} from "../../src/core/python-kernel";
+import { deserializeWebSocketMessage, type JupyterMessage, serializeWebSocketMessage } from "$c/core/python-kernel";
 
 const encoder = new TextEncoder();