docs(config): align environment and credential contracts

Code already treats $DSH_HOME/.env as ordinary launch environment and stores managed credentials in .credentials.yaml, but public docs still described the old store, old precedence, removed literal adapter keys, and the deleted TUI. That directed users to the wrong file and overstated the supported configuration surface.

Update the existing English and Chinese owners in place, document inherited > managed > project > user credential resolution, and record the loadLayeredEnv export. Regenerate only pairing records and the source-line catalog; add no new section or site route.

docs/user/guide/index.md

@@ -11,8 +11,6 @@ Harness implements every capability an AI agent needs—including LLM calls, too
 ```yaml
 # Select the LLM backend
 - name: '@deepseek-ai/dsh-llm-deepseek'
-  config:
-    apiKey: !!js process.env.DEEPSEEK_API_KEY
 
 # Select the one-shot application
 - id: cli-agent