[WIP] Fix JSON schema or generated code for MCP server payload

[Copilot]

Fix MCP Gateway Configuration Validation with Uninterpolated Expressions

Problem

The MCP gateway configuration validation failed when GitHub Actions expressions and backslash-escaped shell variables were present in the generated JSON. The error "invalid character '$' in string escape code" occurred because:

1. Backslash-escaped variables like \${GITHUB_TOKEN} are invalid JSON escape sequences
2. GitHub Actions expressions like ${{ github.workspace }} need to be replaced with sample values for validation
3. The prepareConfigForValidation function didn't handle all variable patterns

Solution

Updated prepareConfigForValidation in pkg/workflow/mcp_renderer.go to handle all patterns:

• Analyze all patterns in the generated config
• Add replacements for backslash-escaped variables (\${...})
  • \${GITHUB_TOKEN}, \${GITHUB_MCP_SERVER_TOKEN}, \${GH_AW_SAFE_INPUTS_API_KEY}, \${GH_AW_SAFE_OUTPUTS_API_KEY}
• Add replacements for GitHub Actions expressions (${{ ... }})
  • ${{ github.workspace }} → /workspace
• Add replacements for unescaped shell variables
  • $GH_AW_SAFE_INPUTS_PORT, $GH_AW_SAFE_OUTPUTS_PORT
• Test the fix with the smoke-copilot workflow - validation error resolved
• Run unit tests - all pass
• Run format and lint - all pass
• Final validation - MCP gateway config validation now works correctly

Testing

• ✅ Compilation with --validate flag no longer shows MCP gateway JSON errors
• ✅ Generated workflow files still contain correct uninterpolated expressions
• ✅ All unit tests pass
• ✅ Code formatting and linting pass

Note: Some integration tests related to action pins failed, but these are unrelated to the MCP gateway configuration validation fix.

Original prompt

Review validation of generated mcp server payload and fix the JSON schema or generated code. You need to take into account uninterpolated expressions:

@pelikhan ➜ /workspaces/gh-aw (main) $ ./gh-aw compile smoke-copilot --validate
⚠ Using experimental feature: safe-inputs
⚠ Generated MCP gateway configuration is not valid JSON: invalid character '$' in string escape code
⚠ Invalid workflow YAML written to: .github/workflows/smoke-copilot.invalid.yml
✗ .github/workflows/smoke-copilot.md:1:1: error: workflow schema validation failed: GitHub Actions schema validation failed: jsonschema validation failed with 'https://json.schemastore.org/github-workflow.json#'

• at '/jobs/conclusion': 'oneOf' failed, none matched
  • at '/jobs/conclusion/steps/0/uses': got null, want string
  • at '/jobs/conclusion': validation failed
    • at '/jobs/conclusion': missing property 'uses'
    • at '/jobs/conclusion': additional properties 'outputs', 'steps', 'runs-on' not allowed
• at '/jobs/detection': 'oneOf' failed, none matched
  • at '/jobs/detection/steps/0/uses': got null, want string
  • at '/jobs/detection': validation failed
    • at '/jobs/detection': missing property 'uses'
    • at '/jobs/detection': additional properties 'runs-on', 'timeout-minutes', 'outputs', 'steps' not allowed
• at '/jobs/pre_activation': 'oneOf' failed, none matched
  • at '/jobs/pre_activation/steps/0/uses': got null, want string
  • at '/jobs/pre_activation': validation failed
    • at '/jobs/pre_activation': missing property 'uses'
    • at '/jobs/pre_activation': additional properties 'runs-on', 'outputs', 'steps' not allowed
• at '/jobs/safe_outputs': 'oneOf' failed, none matched
  • at '/jobs/safe_outputs/steps/0/uses': got null, want string
  • at '/jobs/safe_outputs': validation failed
    • at '/jobs/safe_outputs': missing property 'uses'
    • at '/jobs/safe_outputs': additional properties 'env', 'outputs', 'steps', 'runs-on', 'timeout-minutes' not allowed
• at '/jobs/update_cache_memory': 'oneOf' failed, none matched
  • at '/jobs/update_cache_memory/steps/0/uses': got null, want string
  • at '/jobs/update_cache_memory': validation failed
    • at '/jobs/update_cache_memory': missing property 'uses'
    • at '/jobs/update_cache_memory': additional properties 'runs-on', 'steps' not allowed
• at '/jobs/activation': 'oneOf' failed, none matched
  • at '/jobs/activation/steps/0/uses': got null, want string
  • at '/jobs/activation': validation failed
    • at '/jobs/activation': missing property 'uses'
    • at '/jobs/activation': additional properties 'outputs', 'steps', 'runs-on' not allowed
• at '/jobs/agent': 'oneOf' failed, none matched
  • at '/jobs/agent': validation failed
    • at '/jobs/agent/steps/0/uses': got null, want string
    • at '/jobs/agent/steps/2/uses': got null, want string
  • at '/jobs/agent': validation failed
    • at '/jobs/agent': missing property 'uses'
    • at '/jobs/agent': additional properties 'runs-on', 'env', 'outputs', 'steps' not allowed

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