* Add OpenCode Zen and OpenCode Go provider support
The webui model dropdown had no knowledge of these providers.
When hermes_cli detected them as authenticated, they fell through
to the unknown-provider fallback showing wrong models.
Changes:
- Add opencode-zen and opencode-go to _PROVIDER_DISPLAY
- Add model lists for both to _PROVIDER_MODELS
- Add OPENCODE_ZEN_API_KEY and OPENCODE_GO_API_KEY to env-var fallback detection
- Fix custom:* provider IDs (e.g. custom:my-server) displaying raw ID instead of "Custom"
* Add tests for OpenCode provider registration and detection
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Co-authored-by: David Case <david.case@shruggr.cloud>
12a60faaee