#5808: fix(memory): truncate oversized chunks before embedding

When a single chunk exceeds EMBEDDING_BATCH_MAX_TOKENS, it was pushed to the batch without truncation, causing OpenAI API 400 errors. Now truncates text to fit within the token limit. Fixes #5696 🤖 AI-assisted: Built with Claude Code (claude-opus-4-5) Testing: Fully tested - lint, build, and all tests pass The contributor understands and has reviewed all code changes. <!-- greptile_comment --> <h2>Greptile Overview</h2> <h3>Greptile Summary</h3> This PR fixes a batching edge case in `MemoryIndexManager` where a single `MemoryChunk` larger than `EMBEDDING_BATCH_MAX_TOKENS` was being placed into its own batch without truncation, which could trigger OpenAI 400 errors. The change now truncates the chunk text before pushing it as a single-item batch, keeping batch construction aligned with the embedding API limits. The change is localized to `src/memory/manager.ts` in the embedding batch-building logic used by both the non-batch embedding path and as the fallback path when remote batch embeddings are unavailable/fail. <h3>Confidence Score: 4/5</h3> - This PR is likely safe to merge and addresses a real failure mode, with a small remaining edge case around the truncation heuristic. - The change is small and correctly targets the oversized-single-chunk path in batching, but the truncation is derived from an approximate chars/token constant; depending on how that constant is tuned, truncation may still produce an estimated token count over the max due to rounding, which could reintroduce the original 400s in a corner case. - src/memory/manager.ts (batch truncation math) <!-- greptile_other_comments_section --> _{(4/5) You can add custom instructions or style guidelines for the agent [here](https://app.greptile.com/review/github)!} **Context used:** - Context from `dashboard` - CLAUDE.md ([source](https://app.greptile.com/review/custom-context?memory=fd949e91-5c3a-4ab5-90a1-cbe184fd6ce8)) - Context from `dashboard` - AGENTS.md ([source](https://app.greptile.com/review/custom-context?memory=0d0c8278-ef8e-4d6c-ab21-f5527e322f13)) <!-- /greptile_comment -->