chore: fix lint script for ci

[harshit-cmd]

Description

Fix npm run lint, which was crashing with 8 "TSConfig does not include this file" parse errors and never actually running any rules.

Root cause: .eslintrc.js enables type-aware linting via parserOptions.project: './tsconfig.json', but tsconfig.json excludes src/__tests__/ and *.test.ts/*.spec.ts so tsc doesn't emit tests into dist/. The parser couldn't find type info for test files and bailed before linting anything.

Fix: add a separate tsconfig.eslint.json (extends base, includes tests) and point ESLint at it. The build's tsconfig.json is untouched, so published dist/ output is unchanged.

Changes:

• tsconfig.eslint.json (new): extends tsconfig.json, includes src/**/*, relaxes noUnusedLocals/noUnusedParameters for tests.
• .eslintrc.js: points at tsconfig.eslint.json (with tsconfigRootDir: __dirname); adds an overrides block for src/__tests__/** that enables the jest env and disables type-aware rules that don't apply to tests/mocks (no-unsafe-*, no-explicit-any, require-await, unbound-method, no-extra-semi).
• Mocks: let mockStorage → const; unused options param → _options.

Production source stays under the full strict ruleset including recommended-requiring-type-checking.

Motivation and Context

The lint job in .github/workflows/build.yml runs on every PR but was crashing before it could lint anything — we had no real lint coverage. This restores it.

This is the canonical "split tsconfig" pattern from the typescript-eslint docs for libraries that ship a narrower set of files than they lint.

Related Issue

PR fixes the following issue: N/A — internal CI fix.

Type of change

• Bug fix (non-breaking change which fixes an issue)