Adopt UAPF v2.0.0 cornerstone naming: .bpmn.xml/.dmn.xml/.cmmn.xml -> .bpmn/.dmn/.cmmn [scope-3 3/3]

Renames all 5 cornerstone files to the OMG-ecosystem extensions required
by UAPF-specification v2.0.0, and updates every internal reference:

- uapf.yaml (manifest cornerstone paths + decision refs)
- resources/mappings.yaml (endpoint + usesDecision refs)
- processgit.mcp.yaml (MCP source paths)
- processgit.viewer.json (x2: package + examples)
- cmmn/vertesanas-lieta.cmmn (processTask processRef -> DMN files)
- README.md, docs/source-reference.md, agent.chat.yaml (documentation)

Completes the scope-3 conformance pass for AI-Sandb-Evaluation:
v2.1.0 diagram interchange (CMMN + 3x DMN, prior commits) + v2.0.0 naming.
File contents otherwise unchanged.

processes/L4/vdaa.mi.sandbox.atlase/resources/mappings.yaml

@@ -52,17 +52,17 @@ targets:
   - id: mcp.check_eligibility
     type: mcp_tool
     name: "check_eligibility"
-    endpoint: "dmn/01-atbilstiba-un-izsledzosie.dmn.xml#EligibilityDecision"
+    endpoint: "dmn/01-atbilstiba-un-izsledzosie.dmn#EligibilityDecision"
 
   - id: mcp.calculate_score
     type: mcp_tool
     name: "calculate_score"
-    endpoint: "dmn/02-vertesanas-punkti.dmn.xml#TotalScore"
+    endpoint: "dmn/02-vertesanas-punkti.dmn#TotalScore"
 
   - id: mcp.map_trl
     type: mcp_tool
     name: "map_trl_level"
-    endpoint: "dmn/03-trl-vertejums.dmn.xml#TRLMapping"
+    endpoint: "dmn/03-trl-vertejums.dmn#TRLMapping"
 
 bindings:
   # Phase 1: Registration
@@ -74,7 +74,7 @@ bindings:
   - source: {type: bpmn.businessRuleTask, ref: Task_EligibilityDMN}
     targetId: system.dmn_engine
     mode: autonomous
-    usesDecision: dmn/01-atbilstiba-un-izsledzosie.dmn.xml#EligibilityDecision
+    usesDecision: dmn/01-atbilstiba-un-izsledzosie.dmn#EligibilityDecision
     output: eligibilityResult
 
   # Phase 1b: Deficiency correction
@@ -106,13 +106,13 @@ bindings:
   - source: {type: bpmn.businessRuleTask, ref: Task_TRLMapping}
     targetId: system.dmn_engine
     mode: autonomous
-    usesDecision: dmn/03-trl-vertejums.dmn.xml#TRLMapping
+    usesDecision: dmn/03-trl-vertejums.dmn#TRLMapping
     output: trlScore
 
   - source: {type: bpmn.businessRuleTask, ref: Task_ScoringDMN}
     targetId: system.dmn_engine
     mode: autonomous
-    usesDecision: dmn/02-vertesanas-punkti.dmn.xml#TotalScore
+    usesDecision: dmn/02-vertesanas-punkti.dmn#TotalScore
     output: scoringResult
 
   # Phase 4: Decision