Add enterprise docs structure and include pending core maintenance updates.

docs/features/source-generated-mapping.md

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+# Source-Generated Mapping
+
+## Purpose And Business Outcome
+
+Generate compile-time mapping code to reduce runtime overhead and reflection risk for serialization paths.
+
+## Scope And Non-Goals
+
+Scope:
+- Entity metadata analysis
+- Mapper source generation
+- Collection initialization helpers
+
+Non-goals:
+- Runtime dynamic mapping for unknown schemas
+- Support for unsupported C# patterns outside generator design
+
+## User And System Workflows
+
+1. Consumer defines entities and context patterns.
+2. Build invokes source generator.
+3. Generated mapper code is compiled into target project.
+4. Runtime serialization path uses generated code.
+
+## Interfaces And APIs
+
+- Source generator project under `src/CBDD.SourceGenerators`
+- Attributes in BSON and data-annotation mapping surface
+- Generated initialization methods for context collections
+
+## Permissions And Data Handling
+
+- Generated code can expose field-level mapping behavior.
+- Repository write permissions should be limited to trusted contributors.
+
+## Dependencies And Failure Modes
+
+Dependencies:
+- Roslyn source generator execution during build
+- Entity schema conventions
+
+Failure modes:
+- Missing generation due to invalid entity declarations
+- Serialization mismatch caused by attribute/model changes
+
+## Monitoring, Alerts, And Troubleshooting
+
+- Monitor build output for generator diagnostics.
+- Use [`../runbook.md`](../runbook.md) for escalation.
+- Follow [`../security.md`](../security.md) for review and control expectations.
+- Use [`../troubleshooting.md`](../troubleshooting.md#source-generation-issues) for remediation steps.
+
+## Rollout And Change Considerations
+
+- Generator behavioral changes require broad regression tests across entities.
+- Document any new constraints or unsupported patterns in release notes.
+
+## Validation Guidance
+
+- Run source generator and serialization tests in `tests/CBDD.Tests`.
+- Validate mapper generation with clean `dotnet build` in CI.