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.

docs/data-models.md

@@ -218,6 +218,54 @@ Owner remains empty if unknown.
 
 ---
 
+# Meeting Context V1
+
+Manually maintained YAML metadata scaffold with an implemented Python loader,
+validator and deterministic prompt renderer for chunk extraction.
+
+Top-level structure:
+
+```yaml
+schema_version: "1"
+meeting: {}
+participants: []
+mentioned_people: []
+organization: {}
+known_entities: {}
+context_rules: {}
+```
+
+Meeting Context separates participants, mentioned people, transcript speakers,
+responsible people, roles and departments. It is authoritative only for
+explicitly supplied metadata. It must not be used to infer responsibilities,
+decisions or commitments.
+
+Template:
+
+- `samples/templates/meeting_context.template.yaml`
+
+Documentation:
+
+- `docs/meeting-context.md`
+
+When `--meeting-context` is supplied to extraction, output JSON receives only
+minimal provenance:
+
+```json
+{
+    "context": {
+        "meeting_id": "...",
+        "source_file": "...",
+        "schema_version": "1"
+    }
+}
+```
+
+Later Canonicalizer, Semantic Consolidator, Canonical Meeting Knowledge and
+renderer integration remains planned.
+
+---
+
 # Topic Result
 
 After extraction, every topic contains the collected information.