Implement Meeting Context V1 and extraction improvements

Introduce Meeting Context V1 with YAML schema, validation and template.
Support optional --meeting-context during chunk extraction.
Inject authoritative Meeting Context into extraction prompts.
Record Meeting Context provenance in extraction output.
Activate todos.md in shared prompt assembly.
Strengthen responsibility attribution and decision/todo boundaries.
Add focused Gold scenarios and validation tests.
Update architecture and pipeline documentation.

CHANGELOG.md

@@ -28,6 +28,14 @@
   validation and source fact coverage.
 - Semantic Consolidator V0 benchmark report and consolidated extraction JSON.
 - Gold regression scenario for responsibility attribution integrity.
+- Meeting Context V1 YAML scaffold, generic template and documentation for
+  manually maintained meeting metadata.
+- Meeting Context V1 loader, validator, deterministic prompt representation,
+  optional `--meeting-context` extraction CLI integration and extraction
+  context provenance.
+- PyYAML project dependency for Meeting Context YAML loading.
+- Focused Gold scenarios for responsibility attribution and explicit position
+  extraction.
 
 ### Changed
 
@@ -48,7 +56,12 @@
   views.
 - Updated decision extraction semantics to include explicit process decisions
   and deferrals.
-- Simplified extraction prompt assembly around prompt files.
+- Shared extraction prompt assembly now loads `common.md`, `decisions.md` and
+  `todos.md`.
+- Added explicit action-item responsibility attribution rules and clarified
+  the decision/todo boundary, including duplicate-classification handling.
+- Marked Meeting Context integration with later pipeline stages as planned
+  while extraction-stage integration is implemented.
 
 ### Fixed