feat: workflow enforcement, RAG upgrade, and permission fixes

Task Management:
  - Add cancellation safeguards: require valid reason category (duplicate,
    obsolete, blocked_permanently, reassigned, scope_change, stakeholder_request)
  - Protect active work from arbitrary cancellation - must pause/block first
  - Auto-notify PM when task is blocked with ACTION REQUIRED message
  - PM task scan now shows blocked tasks needing their attention

  Permissions:
  - Add VIEW_STATS to Developer, QA, Documenter, Head Marketing KB permissions
  - Aligns code with docs/workflows/PERMISSIONS.md specification

  RAG/Embeddings:
  - Upgrade embedding model from all-MiniLM-L6-v2 to nomic-embed-text-v1.5
  - 768 dimensions with 8K token context (vs 512 tokens)
  - Add per-index chunk sizes: docs=1536, journals=1024, others=512
  - Switch to fixed chunking (semantic chunking loads separate MiniLM model)
  - Add einops dependency required by nomic model

pyproject.toml

@@ -13,13 +13,11 @@ dependencies = [
     # Core
     "pydantic",
     "pydantic-settings",
-
     # API
     "aiofiles",
     "fastapi",
     "uvicorn[standard]",
     "websockets",
-
     # Database
     "sqlalchemy[asyncio]",
     "asyncpg",  # PostgreSQL async driver
@@ -31,7 +29,6 @@ dependencies = [
 
     # RAG (piragi with PostgreSQL/pgvector backend)
     "piragi[postgres]",
-
     # AI/LLM
     "anthropic",
     "openai",  # For embeddings
@@ -40,7 +37,6 @@ dependencies = [
 
     # MCP (Model Context Protocol)
     "mcp",
-
     # Utilities
     "httpx",
     "python-multipart",
@@ -51,6 +47,7 @@ dependencies = [
 
     # Streaming
     "sse-starlette",  # Server-Sent Events for A2A streaming
+    "einops",
 ]
 
 [project.optional-dependencies]