fix: scope ESLint parserOptions.project to real tsconfigs only

[Copilot]

parserOptions.project: '**/tsconfig.json' is resolved by the TypeScript parser independently of ESLint's ignores — template tsconfigs under **/files/** were still loaded even though those .ts files were excluded from linting. One of those template tsconfigs uses erasableSyntaxOnly (TS 5.5+), which the linter's TypeScript version doesn't recognise, causing a parse error on every linted file.

Changes

• eslint.config.mjs: Replace the wildcard project glob with an explicit list of the three real tsconfigs the linter should operate on.

// before
project: '**/tsconfig.json',

// after
project: ['tsconfig.json', 'packages/ng-schematics/tsconfig.json', 'packages/igniteui-mcp/igniteui-doc-mcp/tsconfig.json'],

Note: !-prefixed negation patterns in parserOptions.project are silently ignored by @typescript-eslint/parser v8, so an explicit allowlist is the only reliable approach here.