fix(gateway): register webhook platform and toolset to fix KeyError on agent runs

[dlkakbs]

What does this PR do?

Webhook-triggered agent runs crashed with KeyError: 'webhook' because the webhook platform had no entry in PLATFORMS (tools_config.py) and no corresponding toolset in TOOLSETS (toolsets.py). When a webhook request was accepted and routed to the gateway, _get_platform_tools() tried to look up PLATFORMS["webhook"] and raised KeyError.

This PR adds the two missing registrations, following the exact same pattern used by every other first-class platform (api_server, telegram, discord, etc.).

Related Issue

Fixes #3773

Type of Change

• 🐛 Bug fix (non-breaking change that fixes an issue)
• ✅ Tests (adding or improving test coverage)

Changes Made

• hermes_cli/tools_config.py: added "webhook" entry to PLATFORMS
• toolsets.py: added "hermes-webhook" toolset using _HERMES_CORE_TOOLS
• tests/gateway/test_webhook_toolset.py: added toolset and platform registration tests (mirrors test_api_server_toolset.py)

How to Test

1. Enable webhook platform in config and start the gateway
2. Configure a static route with secret: INSECURE_NO_AUTH for local testing
3. Send a POST to /webhooks/ — agent run should complete without KeyError: 'webhook'
4. Run pytest tests/gateway/test_webhook_toolset.py -q — all 7 tests pass

Checklist

• My commit messages follow Conventional Commits
• My PR contains only changes related to this fix
• I've run pytest tests/gateway/test_webhook_toolset.py -q and all tests pass
• I've added tests for my changes

Documentation & Housekeeping

• I've updated relevant documentation — N/A
• I've updated cli-config.yaml.example if I added/changed config keys — N/A
• I've considered cross-platform impact — N/A

[teknium1]

Thanks for the contribution! The fix you're proposing here has already landed on main.

Automated hermes-sweeper review found:

• hermes-webhook toolset registered in toolsets.py (lines 443–447) with _HERMES_CORE_TOOLS — exactly as proposed here.
• webhook platform registered in hermes_cli/platforms.py (line 39) with default_toolset="hermes-webhook", folded into PLATFORMS via tools_config.py.
• Both were added by commit e0b2bdb (PR fix: webhook platform support — skip home channel prompt, disable tool progress (salvage #4363) #4660, salvaged from fix: add webhook platform support and skip home channel prompt #4363), merged 2026-04-02 and shipped in v2026.4.3.

The test file (tests/gateway/test_webhook_toolset.py) is the one piece not yet on main. If you'd like to open a focused PR adding just that test coverage, that would be a welcome follow-up!