MCP `app_domains` refuses in the same sentence as the app's settings page and the terminal, not `the domain is refused: invalid_host` #7596

src/http/mcp/tools/app_domains.ts:36 echoes the raw code while the page and the deploys screen say it through domainRefusalText (src/actions/domain_words.ts); the same action should have the same words for a person and an agent.

Done when

• [ ] The MCP tool's refusal message is domainRefusalText(code, …); the error code field is unchanged
• [ ] Success answers carry says from domainAddedText / domainRemovedText / domainSaidText, as the page does
• [ ] test/mcp-app-domains.test.ts asserts, for invalid_host, reserved_host and taken, that MCP's message equals the text the settings page renders for the same refusal

Files: src/http/mcp/tools/app_domains.ts, test/mcp-app-domains.test.ts

Risks. Clients matching the old message text; the code field is what they should match and stays the same.

Suggested brief: mason (a person assigns).