feat: add max chunk size

[joeldierkes]

Note

Medium Risk
SDK 0.77 and ingestion config changes affect how files are chunked and contextualized in production stores; file search now depends on a raw POST path instead of a typed SDK method, so regressions would show up in CLI search and upload behavior rather than compile-time checks alone.

Overview
Extends the CLI for newer store ingestion and search APIs and bumps @mixedbread/sdk from 0.57 to 0.77 (minor CLI release in changeset).

Ingestion controls: store upload and store sync accept --max-chunk-size, validated as a positive integer and passed through upload helpers via new buildFileConfig, which sets max_chunk_size on the upload body (cast on StoreFileConfig because the SDK type does not include that field yet). Upload-related types move from FileCreateParams to StoreFileConfig.

Store creation: store create adds --with-file-context to enable LLM document-level contextualization at create time. buildStoreConfig now builds a ContextualizationConfig object (with_metadata, with_file_context) instead of only true or { with_metadata: fields }, including combining metadata fields with file context.

Search: --file-search no longer calls client.stores.files.search; it POSTs to /v1/stores/files/search with a local response type, since that endpoint is not on the typed client in 0.77.

Tests cover create contextualization combos, sync maxChunkSize wiring, search post calls, and mock file fixtures add content_url for SDK shape updates.

^{Reviewed by Cursor Bugbot for commit bb04032. Bugbot is set up for automated code reviews on this repo. Configure here.}