fix(installer): resolve Antigravity command failures by alignment template names

Investigating the command-loading failures in Antigravity revealed a structural bug introduced in commit 27c18e0. The ConfigDrivenIdeSetup class resolves template names by appending an artifact type suffix to the platform’s template_type, expecting specific files like antigravity-workflow.md or antigravity-agent.md.

Previously, only a generic antigravity.md was provided, causing the loadTemplate() fallback mechanism to silently use default-*.md templates. These default templates inject standard YAML frontmatter (name and quoted description) which Antigravity rejects.

Changes:
- Replaced generic antigravity.md with specific artifact-typed templates (antigravity-agent.md, antigravity-workflow.md, etc.)
- Removed redundant 'name' field from Antigravity templates
- Removed wrapping single quotes from 'description' field to satisfy Antigravity requirements

tools/cli/installers/lib/ide/templates/combined/antigravity-agent.md

@@ -0,0 +1,14 @@
+---
+description: {{description}}
+---
+
+You must fully embody this agent's persona and follow all activation instructions exactly as specified. NEVER break character until given an exit command.
+
+<agent-activation CRITICAL="TRUE">
+1. LOAD the FULL agent file from {project-root}/_bmad/{{path}}
+2. READ its entire contents - this contains the complete agent persona, menu, and instructions
+3. FOLLOW every step in the <activation> section precisely
+4. DISPLAY the welcome/greeting as instructed
+5. PRESENT the numbered menu
+6. WAIT for user input before proceeding
+</agent-activation>

tools/cli/installers/lib/ide/templates/combined/antigravity-task.md

@@ -0,0 +1,9 @@
+---
+description: {{description}}
+---
+
+# {{name}}
+
+Read the entire task file at: {project-root}/{{bmadFolderName}}/{{path}}
+
+Follow all instructions in the task file exactly as written.

tools/cli/installers/lib/ide/templates/combined/antigravity-tool.md

@@ -0,0 +1,9 @@
+---
+description: {{description}}
+---
+
+# {{name}}
+
+Read the entire tool file at: {project-root}/{{bmadFolderName}}/{{path}}
+
+Follow all instructions in the tool file exactly as written.

tools/cli/installers/lib/ide/templates/combined/antigravity-workflow-yaml.md

@@ -0,0 +1,13 @@
+---
+description: {{description}}
+---
+
+IT IS CRITICAL THAT YOU FOLLOW THESE STEPS - while staying in character as the current agent persona you may have loaded:
+
+<steps CRITICAL="TRUE">
+1. Always LOAD the FULL {project-root}/{{bmadFolderName}}/core/tasks/workflow.xml
+2. READ its entire contents - this is the CORE OS for EXECUTING the specific workflow-config {project-root}/{{bmadFolderName}}/{{path}}
+3. Pass the yaml path {project-root}/{{bmadFolderName}}/{{path}} as 'workflow-config' parameter to the workflow.xml instructions
+4. Follow workflow.xml instructions EXACTLY as written to process and follow the specific workflow config and its instructions
+5. Save outputs after EACH section when generating any documents from templates
+</steps>

tools/cli/installers/lib/ide/templates/combined/antigravity-workflow.md

@@ -0,0 +1,5 @@
+---
+description: {{description}}
+---
+
+IT IS CRITICAL THAT YOU FOLLOW THIS COMMAND: LOAD the FULL {project-root}/{{bmadFolderName}}/{{path}}, READ its entire contents and follow its directions exactly!

tools/cli/installers/lib/ide/templates/combined/antigravity.md

@@ -1,8 +0,0 @@
----
-name: '{{name}}'
-description: '{{description}}'
----
-
-Read the entire workflow file at: {project-root}/_bmad/{{workflow_path}}
-
-Follow all instructions in the workflow file exactly as written.