ES-2944 - built-in mocking

[jgrantr]

• new best-of-breed mocking that combines what was being done in the SDK, in the Rithum layers, and in copy/paste code
• written in Typescript
• fully-tested
• markdown doc for coding-assist agents to be able to use it

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Note

Medium Risk
Adds a substantial new mocking layer that overrides core SDK queue read/write, enrich/offload, checkpointing, and S3 stream behavior; while isolated to tests, inaccuracies vs real pipeline semantics could lead to false confidence in unit tests.

Overview
Introduces a new lib/mock-sdk.ts utility that wraps an RStreamsSdk instance with a .mock control surface for unit tests, intercepting queue reads/writes (fromLeo/toLeo/load), checkpointing, cron/bot calls, and optional S3 stream interactions while preserving real stream utilities.

Adds extensive unit + integration coverage (test/lib.mock-sdk.utest.ts) validating end-to-end enrich/offload behavior, spy/capture APIs, reset semantics, and S3 mocking, plus a new lib/mock-sdk.md guide documenting recommended handler-testing patterns and the mock API.

Updates .gitignore to exclude local Claude settings (.claude/settings.local.json).

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Cursor Bugbot has reviewed your changes and found 1 potential issue.

There are 2 total unresolved issues (including 1 from previous review).

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