_build_memory_uri produced URIs of the form:
viking://user/{user}/memories/{subdir}/mem_{slug}.md
The /agent/{agent}/ segment was missing, causing every agent under
the same user to write into the same flat namespace. In multi-agent
deployments agents silently overwrite each other's memories and
vector retrieval cross-pollinates results.
self._agent was already populated correctly (from OPENVIKING_AGENT
env var, default 'hermes') and sent via X-OpenViking-Agent header —
it was simply not interpolated into the URI.
Fix: add the missing segment so URIs follow the documented shape:
viking://user/{user}/agent/{agent}/memories/{subdir}/mem_{slug}.md
Tests: 4 new regression tests in TestOpenVikingMemoryUriBuilder,
13/13 passed (9 existing + 4 new).
c14c37d46b