Add Streaming Execution Protocol to PROTOCOL_SPEC

[tercel]

Summary

Add a Streaming Execution Protocol section to PROTOCOL_SPEC.md defining how modules can support incremental output via an optional stream() method.

Changes

Added new section after ContextFactory Protocol covering:

• Stream semantics: Each yielded record is a partial chunk; complete result is shallow merge of all chunks
• Pipeline: Steps 1-6 identical to call(), then iterate module.stream(), validate accumulated output, run after-middleware
• Fallback: If module lacks stream(), fall back to call() yielding single chunk
• Cross-language signatures: TypeScript AsyncGenerator / Python AsyncIterator
• MCP bridge behavior: Use notifications/progress with progressToken opt-in; final CallToolResult is accumulated result
• Module annotations: annotations.streaming = true declares streaming support

Files Changed

• PROTOCOL_SPEC.md — New "Streaming Execution Protocol" section after line 3885

Source

• tiptap-apcore integration finding: streaming is a generic capability needed across all apcore consumers