Remove two-file workflow structure from documentation templates

[Copilot]

Documentation templates were instructing users to split workflows into two files: configuration in .github/workflows/ and prompts in .github/agentics/. This has been simplified to a single-file structure.

Changes

• create-agentic-workflow.md: Removed "Two-File Structure" section and all references to .github/agentics/ directory
• update-agentic-workflow.md: Removed separate file editing guidance and runtime-import references
• Workflow structure: Now documented as single markdown file containing both YAML frontmatter (configuration) and markdown body (agent prompt)
• Recompilation: All workflow changes now consistently require gh aw compile <workflow-id>

Before

### File 1: `.github/agentics/<workflow-id>.md` (Agent Prompt)
- Edit without recompilation
- Changes take effect immediately

### File 2: `.github/workflows/<workflow-id>.md` (Config + Import)
---
description: Example workflow
---
{{#runtime-import agentics/<workflow-id>.md}}

After

### File: `.github/workflows/<workflow-id>.md`
---
description: Example workflow
---

# Workflow Name

Complete agent prompt and instructions here...

Net reduction: 251 lines removed from documentation templates.

Original prompt

Update to the create-agentic-workflows.md and update-agentic-workflows.md documents.

Remove prompting to place the body of the markdown in a separate file .github/agentics/* and instead just use the current markdown file. Remove any prompting encouraging this behavior.

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