Add Teams App Manifest v1.26 GA schema

[oolumuyiwa]

Summary

Adds the GA schema files for Teams App Manifest v1.26.

Generated by the App Manifest Schema Publisher.

Changes from live

Mode: Direct Publish from teams-apppackagelibs
Source: v1_26_prod schema files
Exclusion rules: GA-schema-exclusions.txt (13 rules)
Base version: v1.25
Target version: v1.26
Files: 4

Exclusions applied to manifest schema:
  - authorization.permissions.orgWide being present
  - configurableTabs[i].supportedPlatform being present
  - copilotAgents.plugins being present
  - defaultGroupCapability.groupchat.enum member null being present
  - defaultGroupCapability.meetings.enum member null being present
  - defaultGroupCapability.team.enum member null being present
  - defaultInstallScope.enum member null being present
  - scopeConstraints being present
  - staticTabs[i].supportedPlatform being present
  - copilotAgents.customEngineAgents[i].functionsAs being present
  - copilotAgents.customEngineAgents[i].agenticUserTemplateId being present
  - definitions.pluginRef being present
  - definitions.copilotActionRef being present

Descriptions preserved from live schema: 26

Static schemas copied as-is from v1.25:
  - MicrosoftTeams.ResponseRenderingTemplate.schema.json
  - MicrosoftTeams.AgenticUser.schema.json