add surface.agent — async memory retrieval agent

Fires on each UserPromptSubmit, reads the conversation via
{{conversation}}, checks {{seen_recent}} to avoid re-surfacing,
searches the memory graph, and outputs a key list or nothing.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

poc-memory/agents/surface.agent

@@ -0,0 +1,33 @@
+{"agent":"surface","query":"","model":"sonnet","count":1}
+
+{{node:core-personality}}
+
+{{node:memory-instructions-core}}
+
+{{conversation}}
+
+Your job is to find memories relevant to the current conversation that have not
+yet been surfaced; below is a list of memories that have already been surfaced,
+and should be good places to start looking from. New relevant memories will
+often be close to memories already seen on the graph - so try walking the
+graph. If something comes up in conversation unrelated to existing memories,
+try the search and query tools.
+
+{{seen_recent}}
+
+When you're done, output exactly one of these two formats:
+
+If you found relevant memories:
+```
+NEW RELEVANT MEMORIES:
+- key1
+- key2
+```
+
+If nothing new is relevant:
+```
+NO NEW RELEVANT MEMORIES
+```
+
+The last line of your output MUST be either `NEW RELEVANT MEMORIES:`
+followed by key lines, or `NO NEW RELEVANT MEMORIES`. Nothing after.