[WIP] Fix environment variable expansion for safeinputs MCP server

[Copilot]

Plan: Fix Environment Variable Expansion in Safe-Inputs MCP Server Configuration

The generated MCP configuration for the safeinputs server using Copilot contains unexpanded environment variables (${GH_AW_SAFE_INPUTS_PORT} instead of the actual port value), causing connection failures.

Root Cause

When the MCP config JSON file is created with heredoc (cat > file << EOF), environment variable placeholders like \${GH_AW_SAFE_INPUTS_PORT} are written literally. JSON doesn't expand shell variables, so when Copilot reads the config, it sees the literal string ${GH_AW_SAFE_INPUTS_PORT} instead of the actual port value.

Solution

• Understand the current code flow
• Add sed commands in PostEOFCommands to replace variable placeholders with actual values
• Update safe_inputs.go to use consistent placeholder format
• Add/update tests to verify the fix
• Run full test suite and build
• Manual verification

Original prompt

The generated configuration for the safeinputs mcp server using copilot is incorrect. The environment variables are not expanded (GH_AW_SAFE_INPUTS_PORT)

2025-12-08T02:33:20.103Z [LOG] Starting remote MCP client for safeinputs with url: http://host.docker.internal:${GH_AW_SAFE_INPUTS_PORT}
2025-12-08T02:33:20.104Z [LOG] Starting MCP client for safeoutputs with
command: node
args: /tmp/gh-aw/safeoutputs/mcp-server.cjs
cwd: /home/runner/work/gh-aw/gh-aw
2025-12-08T02:33:20.104Z [LOG] Starting MCP client for safeoutputs with command: node and args: /tmp/gh-aw/safeoutputs/mcp-server.cjs
2025-12-08T02:33:20.104Z [LOG] Creating MCP client for safeoutputs...
2025-12-08T02:33:20.109Z [LOG] Connecting MCP client for safeoutputs...
2025-12-08T02:33:20.113Z [ERROR] Failed to start MCP client for remote server safeinputs: TypeError: Invalid URL

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[pelikhan]

@copilot look how it is done for github mcp server "remote" mode