Clear stale base_url on gateway model switches

[ipriyaaanshu]

What does this PR do?

Clears stale inline model.base_url values when gateway model switches persist non-custom providers.

This is a focused follow-up to merged PR #49380. That PR added shared stale endpoint cleanup and wired it into gateway model-switch persistence, but the shared helper clears api_key, legacy api, and api_mode only. It does not clear base_url, so a gateway /model switch can still re-save an old inline endpoint for a built-in provider.

In my local repro, switching models from Telegram rewrote config.yaml with:

model:
  default: minimax-m3
  provider: opencode-go
  base_url: https://opencode.ai/zen/go

The provider profile endpoint is https://opencode.ai/zen/go/v1, so later gateway-spawned agents inherited the stale inline endpoint and failed even though TUI/direct provider calls worked.

This PR keeps existing helper behavior backward-compatible by making base_url clearing opt-in, then enables it only in the gateway persistence paths for non-custom providers.

Relationship to existing work

• Completes the remaining base_url cleanup gap from fix(model): clear stale endpoint credentials across all provider switches #49380 for gateway model switches.
• Targets the current gateway/slash_commands.py persistence paths, not the older gateway/run.py path referenced by some historical PRs.
• Complements fix: prevent stale base_url after provider switch #47533: that PR adds runtime-provider protection against stale stock endpoints, while this PR prevents the gateway from persisting the stale inline endpoint in the first place.
• The duplicate issue I opened (Gateway model switches persist stale base_url for built-in providers #51486) has been closed in favor of canonical issue [Bug]: Gateway /model switch leaves stale base_url and does not persist api_mode #25107.

Related Issue

Fixes #25107

Refs #47533 and #51486.

Type of Change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Security fix
• Documentation update
• Tests (adding or improving test coverage)
• Refactor (no behavior change)
• New skill (bundled or hub)

Changes Made

• hermes_cli/config.py: add optional clear_base_url support to clear_model_endpoint_credentials(...).
• gateway/slash_commands.py: clear inline base_url when persisting gateway model switches for non-custom providers.
• tests/gateway/test_model_picker_persist.py: assert picker-based built-in provider switches do not persist model.base_url.
• tests/gateway/test_model_command_flat_string_config.py: assert typed /model built-in provider switches do not persist model.base_url.

How to Test

1. Run the focused gateway regression tests:

   python -m pytest tests/gateway/test_model_picker_persist.py tests/gateway/test_model_command_flat_string_config.py -q

2. Confirm the result:

   8 passed, 2 warnings
   

3. Manual repro used before this patch: switch an opencode-go model from Telegram and inspect config.yaml; the stale root model.base_url was reintroduced before this fix.

Checklist

Code

• I have read the Contributing Guide
• My commit messages follow Conventional Commits (fix(scope):, feat(scope):, etc.)
• I searched for existing PRs to make sure this is not a duplicate
• My PR contains only changes related to this fix/feature (no unrelated commits)
• I have run pytest tests/ -q and all tests pass
• I have added tests for my changes (required for bug fixes, strongly encouraged for features)
• I have tested on my platform: Ubuntu 24.04.4 LTS

Documentation & Housekeeping

• I have updated relevant documentation (README, docs/, docstrings) - or N/A
• I have updated cli-config.yaml.example if I added/changed config keys - or N/A
• I have updated CONTRIBUTING.md or AGENTS.md if I changed architecture or workflows - or N/A
• I have considered cross-platform impact (Windows, macOS) per the compatibility guide - or N/A
• I have updated tool descriptions/schemas if I changed tool behavior - or N/A

For New Skills

N/A

Screenshots / Logs

Sanitized failing endpoint before the fix:

Provider: opencode-go
Endpoint: https://opencode.ai/zen/go
Error: APIConnectionError / HTTP 404 depending on attempt

[teknium1]

Salvaged and merged via PR #53977 (#53977). Your commit was cherry-picked onto current main with your authorship preserved (commit f6deabc), bundled with the opencode-zen picker catalog fix from #49129 since both came from the same model-picker report. The base_url clear logic merged as-is. Thanks!