refactor: standardize reset method name to resetDefaults in context mock

Author: virgofx

.github/agents/test-specialist.agent.md

@@ -21,7 +21,7 @@ Before writing or modifying tests, read `docs/testing.md` for the full mock arch
 1. `__mocks__/@actions/core.ts` — Global replacement. Logging silenced. `getInput`/`getBooleanInput` use real
    implementations (read `INPUT_*` env vars)
 2. `__mocks__/config.ts` — Proxy mock: `.set({...})` to override, `.resetDefaults()` to restore
-3. `__mocks__/context.ts` — Proxy mock: `.set({...})`, `.reset()`, `.useRealOctokit()`, `.useMockOctokit()`
+3. `__mocks__/context.ts` — Proxy mock: `.set({...})`, `.resetDefaults()`, `.useRealOctokit()`, `.useMockOctokit()`
 
 ## Test Helpers