Agent-aware provenance for memory tools

Add provenance field to Agent, set to "agent:{name}" for forked
subconscious agents. Memory tools (write, link_add, supersede,
journal_new, journal_update) now read provenance from the Agent
context when available, falling back to "manual" for interactive use.

AutoAgent passes the forked agent to dispatch_with_agent so tools
can access it.

Co-Authored-By: Proof of Concept <poc@bcachefs.org>

src/agent/oneshot.rs

@@ -355,7 +355,11 @@ impl AutoAgent {
                 }
                 format!("{}: {}", key, value)
             } else {
-                agent_tools::dispatch(&call.function.name, &args).await
+                let agent = match &*backend {
+                    Backend::Forked(a) => Some(a.clone()),
+                    _ => None,
+                };
+                agent_tools::dispatch_with_agent(&call.function.name, &args, agent).await
             };
 
             dbglog!("[auto] {} result: {} chars", self.name, output.len());