refactor: improve type safety and strengthen extension tests

- Fix unsafe non-null assertions by properly handling undefined
  activeTextEditor in getActiveSelectionLocation and related methods
- Add eslint-disable comments with justifications for necessary
  non-null assertions
- Refactor extension tests to verify actual behavior (persisted data)
  instead of only checking command execution success
- Remove redundant unit tests superseded by integration tests
- Update pre-commit hook to fail on ESLint warnings
- Add pretest:ext script to ensure compilation before extension tests

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <[email protected]>

Author: fegge

.husky/pre-commit

@@ -1,8 +1,8 @@
 #!/bin/sh
 
-# Run ESLint on src/
+# Run ESLint on src/ (fail on warnings too)
 echo "Running ESLint..."
-npm run lint
+npm run lint -- --max-warnings 0
 if [ $? -ne 0 ]; then
     echo "ESLint failed. Please fix the errors before committing."
     exit 1

.vscode-test.mjs

@@ -1,11 +1,14 @@
 import { defineConfig } from "@vscode/test-cli";
+import * as path from "path";
 
 export default defineConfig({
-    files: "out/test/extension/**/*.test.js",
+    files: "out/test/extension/suite/**/*.test.js",
     version: process.env.VSCODE_VERSION || "stable",
+    workspaceFolder: path.resolve("test/extension/fixtures/sample-workspace"),
     mocha: {
-        ui: "bdd",
+        ui: "tdd",
         timeout: 60000,
     },
-    launchArgs: ["--disable-extensions", "--disable-gpu"],
+    launchArgs: ["--disable-extensions", "--disable-gpu", "--disable-workspace-trust"],
+    extensionDevelopmentPath: path.resolve("."),
 });