feat(caas): port production Context-as-a-Service features from internal repo

New source files:
- enrichment.py (124L): MetadataEnricher solving the Flat Chunk Fallacy
- pragmatic_truth.py (434L): SourceDetector, ConflictDetector, CitationFormatter
- gateway/trust_gateway.py (455L): Enterprise-grade private cloud router with audit
- ingestion/structure_parser.py (183L): Content tier assignment (High/Medium/Low)

Updated init files:
- gateway/__init__.py: Re-export TrustGateway and security models
- ingestion/__init__.py: Re-export StructureParser

New test files:
- test_pragmatic_truth.py (305L): Source detection and conflict resolution tests
- test_context_triad.py (364L): Hot/warm/cold context management tests

106 tests pass (+14 new), 0 regressions from pre-existing baseline.

Closes #58

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: imran-siddique

packages/agent-os/modules/caas/src/caas/enrichment.py

@@ -0,0 +1,130 @@
+# Copyright (c) Microsoft Corporation.
+# Licensed under the MIT License.
+
+"""
+Metadata enrichment module for contextual injection.
+
+Solves the "Flat Chunk Fallacy" by enriching chunks with parent metadata.
+Instead of storing isolated chunks like "It increased by 5%", we store:
+"[Document: Q3 Earnings] [Chapter: Revenue] [Section: North America] It increased by 5%."
+
+This ensures the vector carries the weight of its context.
+"""
+
+from typing import List, Optional
+from caas.models import Section, Document, DocumentType
+
+
+class MetadataEnricher:
+    """
+    Enriches sections with parent metadata for contextual awareness.
+    
+    Transforms isolated chunks into context-aware chunks by injecting
+    hierarchical metadata (document, chapter, section).
+    """
+    
+    def enrich_sections(self, document: Document) -> List[Section]:
+        """
+        Enrich all sections in a document with metadata prefixes.
+        
+        Args:
+            document: Document with sections to enrich
+            
+        Returns:
+            List of enriched sections
+        """
+        enriched_sections = []
+        
+        for section in document.sections:
+            enriched_section = self._enrich_section(section, document)
+            enriched_sections.append(enriched_section)
+        
+        return enriched_sections
+    
+    def _enrich_section(self, section: Section, document: Document) -> Section:
+        """
+        Enrich a single section with metadata prefix.
+        
+        Args:
+            section: Section to enrich
+            document: Parent document
+            
+        Returns:
+            Section with enriched content
+        """
+        # Build metadata prefix
+        metadata_parts = []
+        
+        # Add document title
+        metadata_parts.append(f"[Document: {document.title}]")
+        
+        # Add document type if meaningful
+        if document.detected_type and document.detected_type.value != "unknown":
+            doc_type_display = document.detected_type.value.replace("_", " ").title()
+            metadata_parts.append(f"[Type: {doc_type_display}]")
+        
+        # Add chapter/parent section if available
+        if section.chapter:
+            metadata_parts.append(f"[Chapter: {section.chapter}]")
+        elif section.parent_section:
+            metadata_parts.append(f"[Parent: {section.parent_section}]")
+        
+        # Add current section
+        metadata_parts.append(f"[Section: {section.title}]")
+        
+        # Build enriched content
+        metadata_prefix = " ".join(metadata_parts)
+        enriched_content = f"{metadata_prefix} {section.content}"
+        
+        # Create a new section with enriched content
+        # We preserve the original section but update the content
+        # Note: Using model_copy() from Pydantic v2 (we're on v2.5.0)
+        enriched_section = section.model_copy()
+        enriched_section.content = enriched_content
+        
+        return enriched_section
+    
+    def get_enriched_chunk(
+        self, 
+        section: Section, 
+        document_title: str,
+        document_type: Optional[DocumentType] = None,
+        include_type: bool = True
+    ) -> str:
+        """
+        Get an enriched chunk string for a section.
+        
+        Useful for building enriched context on-the-fly without modifying
+        the stored section.
+        
+        Args:
+            section: Section to enrich
+            document_title: Title of parent document
+            document_type: Type of document (optional)
+            include_type: Whether to include document type in prefix
+            
+        Returns:
+            Enriched chunk string
+        """
+        metadata_parts = []
+        
+        # Add document title
+        metadata_parts.append(f"[Document: {document_title}]")
+        
+        # Add document type if requested and available
+        if include_type and document_type and document_type.value != "unknown":
+            doc_type_display = document_type.value.replace("_", " ").title()
+            metadata_parts.append(f"[Type: {doc_type_display}]")
+        
+        # Add hierarchical context
+        if section.chapter:
+            metadata_parts.append(f"[Chapter: {section.chapter}]")
+        elif section.parent_section:
+            metadata_parts.append(f"[Parent: {section.parent_section}]")
+        
+        # Add current section
+        metadata_parts.append(f"[Section: {section.title}]")
+        
+        # Build and return enriched content
+        metadata_prefix = " ".join(metadata_parts)
+        return f"{metadata_prefix} {section.content}"

packages/agent-os/modules/caas/src/caas/gateway/__init__.py

@@ -1,9 +1,27 @@
 # Copyright (c) Microsoft Corporation.
 # Licensed under the MIT License.
-# Community Edition — basic context/memory management
 """
-Gateway sub-package — placeholder after Trust Gateway removal.
+Trust Gateway: Enterprise-Grade Private Cloud Router
+
+The enterprise-ready gateway that can be deployed on-premises or in private cloud
+to address CISO concerns about data security and privacy.
 """
 
-__all__: list = []
+from caas.gateway.trust_gateway import (
+    TrustGateway,
+    DeploymentMode,
+    SecurityPolicy,
+    SecurityLevel,
+    AuditLog,
+    DataRetentionPolicy
+)
+
+__all__ = [
+    "TrustGateway",
+    "DeploymentMode",
+    "SecurityPolicy",
+    "SecurityLevel",
+    "AuditLog",
+    "DataRetentionPolicy"
+]