fix: update validation to accept minimal server environment without inference models

[jiannnnyyyyy]

Which issue or RFC does this PR close?

Closes #1442.

Rationale for this change

powercontext config validate --env-file incorrectly required a complete inference configuration, even when the environment file was only intended to configure a minimal Server.

This made valid configurations accepted by powercontext server run --env-file fail validation because no generation model was configured.

What changes are included in this PR?

• Allow config validate to validate minimal Server-only environment files without inference models.
• Keep strict validation for complete configurations generated by config init.
• Validate provider models only when inference models are configured.
• Ensure env-file validation ignores stale POWERCONTEXT_SERVER_* values from the shell.
• Add a regression test covering the seekDB, HTTP, and Dashboard configuration from issue bug: powercontext config validate rejects a server-runnable env file when inference models are not configured #1442.
• Update English and Chinese configuration documentation.

Are there any user-facing changes?

Yes. powercontext config validate --env-file now accepts valid minimal Server configurations that do not configure inference models.

There are no breaking API changes or persistence format changes.

How was this change tested?

• pytest -q tests/test_config_cli.py -k 'not init_validate_and_show_round_trip_managed_environment'
  • 22 passed
• Manual validation using the exact issue scenario:
  • seekDB
  • 127.0.0.1
  • port 8888
  • multiple Dashboard scopes
  • no inference models configured
• Ruff linting and formatting checks
• Ty type checking
• zensical build --strict

The skipped existing test checks Unix file permissions and is not portable on Windows.

AI usage statement

This PR was developed with OpenAI Codex using the GPT-5 model. The AI assisted with repository inspection, implementation, test updates, documentation updates, and validation.

[CLAassistant]

All committers have signed the CLA.

[Teingi]

Thanks for addressing #1442. I reproduced the minimal success case, but the current head still has runtime-parity gaps and conflicts with the latest master (259bee3).

[Teingi]

resolve conflicts

[Teingi]

LGTM