#2071: fix: accept JSON string for cron.add job parameter (#1940)

gh pr create --title "fix: accept JSON string for cron.add job parameter (#1940)" --body " ## Summary - Parse job parameter as JSON string when passed as string instead of object - Fixes inconsistent 'must be object' error when AI tools pass job as JSON string ## Testing - Added test: accepts cron.add job payloads as JSON strings - All 16 cron-tool tests pass - pnpm lint ✅ - pnpm build ✅ ## AI/Vibe-Coded PR 🤖 - [x] Mark as AI-assisted in the PR title or description - [x] Note the degree of testing: **fully tested locally** - [x] Include prompts or session logs if possible: available on request - [x] Confirm you understand what the code does ### AI Tools Used - Claude Opus-4.5 - Cursor IDE - Manual review performed Fixes #1940" <!-- greptile_comment --> <h2>Greptile Overview</h2> <h3>Greptile Summary</h3> This PR makes the `cron` agent tool more tolerant of AI/client callers by accepting `job` as a JSON-encoded string for the `cron.add` action. The implementation parses `job` when it’s a string, validates it is a plain object (not null/array), then continues through existing normalization (`normalizeCronJobCreate`) and defaulting behavior before calling the gateway. A new Vitest case covers passing `job` as a JSON string and asserts the tool still emits the same normalized `cron.add` request payload as when an object is provided. <h3>Confidence Score: 4/5</h3> - This PR is likely safe to merge; changes are localized and covered by a new test. - The change only affects the `cron.add` branch by adding a small JSON-parse path and a stricter plain-object guard, with a new unit test validating the intended behavior. Main remaining risk is minor: the tool schema still advertises `job` as an object, so some tool runtimes may reject string input before it reaches this runtime parsing path. - src/agents/tools/cron-tool.ts <!-- greptile_other_comments_section --> _{(5/5) You can turn off certain types of comments like style [here](https://app.greptile.com/review/github)!} <!-- /greptile_comment -->