Introduce X-KILOCODE-FEATURE header for tracking request origin
across different entry points (CLI, VSCode extension, autocomplete).
- Add HEADER_FEATURE, DEFAULT_FEATURE, and ENV_FEATURE constants
- Add getFeatureHeader() helper reading from KILOCODE_FEATURE env var
- Include feature header in buildKiloHeaders() when env var is set
- Set feature to "autocomplete" for FIM/completion requests
- Set KILOCODE_FEATURE="vscode-extension" when spawning CLI from VSCode
- Default to "cli" feature in opencode entry point
- Add unit tests for feature header logic
Pedro Heyerdahl
0f139f3120