The .usage.json file is owned by hermes-agent (tools/skill_usage.py).
This change removes the webui-side increment logic to avoid:
1. File ownership conflict - both writing to same file
2. Schema mismatch - agent uses ISO strings, webui used floats
3. Concurrency issues - agent uses fcntl locks, webui had no locking
4. Double-counting - agent already increments counters server-side
Changes:
- api/skill_usage.py: keep only read_skill_usage(), remove increment functions
- api/streaming.py: remove skill usage counter hook
- api/routes.py: adapt response to pass through agent's format as-is,
with defensive coercion for None values and metadata preservation
- tests/test_skill_usage.py: remove increment tests (17→7 cases)