test(ai-evals): add Mocha + Chai + Sinon test suite for runExperiment

Adds a unit test suite matching sibling action conventions:
- 8 tests covering all RunResult status branches (NOT_FOUND, CREATE_FAILED,
  FAILED, PASS, REGRESSION) and exit codes (0/1/2/3)
- Stubs the SDK at its method boundary so tests are deterministic, fast,
  and isolated from network/auth concerns
- Asserts CI metadata pass-through to experimentRuns.create as the 5th arg
- Asserts lifecycle progress messages

Tooling:
- mocha + chai + sinon + nyc (matches setup-env / setup-local / browserstack-report-action)
- ts-node loader so Mocha can read .ts source directly
- @typescript-eslint v8 (supports TypeScript 5.9)
- husky pre-commit hook: runs test + build + stages dist/ so src and dist
  cannot drift in a published commit

'npm test' chains tsc --noEmit -> eslint -> nyc mocha with HTML coverage
report (coverage/index.html, gitignored).

Author: EMMUUU28

ai-evals/.eslintrc.json

@@ -0,0 +1,19 @@
+{
+  "root": true,
+  "parser": "@typescript-eslint/parser",
+  "plugins": ["@typescript-eslint"],
+  "extends": [
+    "eslint:recommended",
+    "plugin:@typescript-eslint/recommended"
+  ],
+  "env": {
+    "node": true,
+    "es2022": true,
+    "mocha": true
+  },
+  "rules": {
+    "@typescript-eslint/no-explicit-any": "off",
+    "@typescript-eslint/no-unused-vars": ["error", { "argsIgnorePattern": "^_" }]
+  },
+  "ignorePatterns": ["dist/", "node_modules/", "coverage/"]
+}

ai-evals/.gitignore

@@ -1,2 +1,4 @@
 node_modules/
 *.log
+.nyc_output/
+coverage/