Config parser crashes on malformed JSON instead of recovering gracefully

[suryaiyer95]

Bug

When the config file (~/.config/altimate-code/altimate-code.json) contains malformed JSON, altimate-code crashes with a raw JSONC parse error instead of recovering gracefully.

Steps to Reproduce

1. Have a malformed config file at ~/.config/altimate-code/altimate-code.json:

{
  "$schema": "https://altimate-code.dev/config.json",
  "mcp": {
      }
    }
  }
}

2. Run altimate-code -s ses_...
3. Get a crash:

Error: Config file at /Users/surya/.config/altimate-code/altimate-code.json is not valid JSON(C):
--- JSONC Input ---
...
--- Errors ---
EndOfFileExpected at line 6, column 3

Expected Behavior

• Warn the user about the invalid config and fall back to defaults, OR
• Provide a clear, actionable error message (e.g., "Your config file has a syntax error on line 6. Fix it or delete it to use defaults.")

Context

This can happen when a user partially edits their config (e.g., removes an MCP server entry but leaves behind extra closing braces). The current error dump with --- JSONC Input --- / --- Errors --- formatting is developer-facing, not user-facing.