Documentation changes

This PR keeps /docs in sync with code merged into main in the last 36 hours.

PR #4357 — feat(wasm): shared runtime, portable tools, in-memory storage, egress proxy, and cloud provider builds

That PR already updated docs/guides/go-sdk/index.md for most of its user-facing Go API additions (embeddedchat opt-in behaviors, in-memory RAG documents, Vertex AI transport-wrapper/token-source authentication). Reviewing the full diff surfaced one additional public API that the existing MCP OAuth Token Persistence section did not yet cover:

• Added a "Session-scoped token stores" subsection documenting the new mcp.WithOAuthTokenStore context helper, which lets embedders hosting multiple isolated sessions in one process (e.g. a server or the new wasm bridge) give each session its own OAuth token store instead of sharing the process-wide default.

No other /docs pages were found to be inaccurate, incomplete, or missing as a result of this PR — the remaining code changes are either internal refactors with no behavior change for existing documented paths (browser/js-only build-tag splits of add_environment_info, limit_large_tool_results, the memory toolset, Bedrock AWS config, the fzf fuzzy-matching extraction) or are already fully documented in cmd/wasm/README.md, which is outside /docs.

Source PRs

• feat(wasm): shared runtime, portable tools, in-memory storage, egress proxy, and cloud provider builds #4357