#14483: fix(cli-runner): map Anthropic cache_creation_input_tokens

## Summary - map `usage.cache_creation_input_tokens` to `cacheWrite` in `toUsage()` - keep existing aliases (`cache_write_input_tokens`, `cacheWrite`) intact - add a unit test for usage normalization to prevent regression ## Why Anthropic reports cache creation usage under `cache_creation_input_tokens`. Without this mapping we under-report cache write tokens. Closes #14366 ## Validation - [x] `npx pnpm build` - [x] `npx pnpm check` - [x] `npx pnpm exec vitest run src/agents/cli-runner/helpers.test.ts` ## AI assistance - [x] AI-assisted - Testing: locally validated with targeted and repo checks above <!-- greptile_comment --> <h2>Greptile Overview</h2> <h3>Greptile Summary</h3> This PR updates the CLI runner’s usage normalization so that Anthropic’s `usage.cache_creation_input_tokens` is counted as `cacheWrite` (in addition to the existing aliases), and adds a small Vitest unit test to prevent regressions in the JSON parsing path. The change is localized to `src/agents/cli-runner/helpers.ts`’s `toUsage()` normalization logic, which feeds `parseCliJson()` and therefore impacts how token usage is reported across CLI backends. <h3>Confidence Score: 4/5</h3> - This PR is low-risk and likely safe to merge after tightening the new test fixture to avoid type-unsafe configuration casting. - The production change is a straightforward additional alias mapping in `toUsage()` and is covered by a targeted unit test. The main concern is the new test using an empty object cast to `CliBackendConfig`, which can hide future breaking changes to required config fields and reduce the test’s value. - src/agents/cli-runner/helpers.test.ts <!-- greptile_other_comments_section --> _{(4/5) You can add custom instructions or style guidelines for the agent [here](https://app.greptile.com/review/github)!} <!-- /greptile_comment -->