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-display.test.ts

@@ -1,5 +1,5 @@
 import { describe, expect, it } from "bun:test";
-import { type KernelDisplayOutput, PythonKernel } from "../../src/core/python-kernel";
+import { type KernelDisplayOutput, PythonKernel } from "$c/core/python-kernel";
 
 const renderDisplay = (
 	PythonKernel as unknown as {