[Feature] Fix Mocha `this` typing in smoke test dispose hooks

[EmmaYuan1015]

• Problem:
  • TS next reports TS2683: 'this' implicitly has type 'any' in smoke suite dispose functions.
• Current locations:
  • test/smoke/suites/actionBar.test.ts
  • test/smoke/suites/commands.test.ts
  • test/smoke/suites/debugConfiguration.test.ts
  • test/smoke/suites/fileExplorer.test.ts
  • test/smoke/suites/packager.test.ts
• Proposed change:
  • Type hook context explicitly, e.g. async function dispose(this: Mocha.Context) { ... }.
  • Ensure @types/mocha usage is consistent in smoke project.
• Acceptance criteria:
  • TS2683 is removed for all dispose hooks.
  • Smoke test behavior is unchanged (screenshots still taken on failures).