fix(cli): merge prompt_caching config category into agent

[LeonSGP43]

Summary

• merge the standalone prompt_caching schema category into agent
• remove the last single-field dashboard config category
• keep the change scoped to web config schema generation only

Why

The shared Tests / test backlog is red on tests/hermes_cli/test_web_server.py::TestBuildSchemaFromConfig::test_no_single_field_categories because prompt_caching is still emitted as its own one-field category.

Verification

• python3 - <<"PY" ... checked CONFIG_SCHEMA category counts
• confirmed prompt_caching count is gone and no category has fewer than 2 fields

[teknium1]

Closing as already fixed on main.

Triage notes (high confidence):
The exact one-line change ("prompt_caching": "agent", in CATEGORY_RENAMES) is already on origin/main hermes_cli/web_server.py:362.

If you still see this on the latest version, please reopen with reproduction steps.

(Bulk-closed during a CLI triage sweep.)