provenance: set POC_PROVENANCE for agent subprocesses, Jaccard initial strength

Agent subprocess calls now set POC_PROVENANCE=agent:{name} so any
nodes/links created via tool calls are tagged with the creating agent.
This makes agent transcripts indistinguishable from conscious sessions
in format — important for future model training.

new_relation() now reads POC_PROVENANCE env var directly (raw string,
not enum) since agent names are dynamic.

link-add now computes initial strength from Jaccard similarity instead
of hardcoded 0.8. New links start at a strength reflecting actual
neighborhood overlap.

Co-Authored-By: Kent Overstreet <kent.overstreet@linux.dev>

poc-memory/src/store/types.rs

@@ -560,7 +560,8 @@ pub fn new_visit(node_uuid: [u8; 16], node_key: &str, agent: &str, outcome: &str
 
 pub(crate) fn visits_path() -> PathBuf { memory_dir().join("visits.capnp") }
 
-/// Create a new relation
+/// Create a new relation.
+/// Provenance is set from POC_PROVENANCE env var if present, else "manual".
 pub fn new_relation(
     source_uuid: [u8; 16],
     target_uuid: [u8; 16],
@@ -569,6 +570,9 @@ pub fn new_relation(
     source_key: &str,
     target_key: &str,
 ) -> Relation {
+    // Use raw env var for provenance — agent names are dynamic
+    let provenance = std::env::var("POC_PROVENANCE")
+        .unwrap_or_else(|_| "manual".to_string());
     Relation {
         uuid: *Uuid::new_v4().as_bytes(),
         version: 1,
@@ -577,7 +581,7 @@ pub fn new_relation(
         target: target_uuid,
         rel_type,
         strength,
-        provenance: "manual".to_string(),
+        provenance,
         deleted: false,
         source_key: source_key.to_string(),
         target_key: target_key.to_string(),