journal_new: separate name from title, dedup keys

- journal_new(name, title, body): name becomes the node key,
  title goes in the ## heading. Agent picks short searchable names.
- Auto-dedup: if the key exists, append -2, -3, etc.
- CLI journal write also requires a name argument now.

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

src/subconscious/agents/surface-observe.agent

@@ -106,7 +106,7 @@ First, check the previous entry:
   journal_tail()
 
 To start a new entry when the subject has changed:
-  journal_new("title", "body")
+  journal_new("short-key-name", "Descriptive title for heading", "body")
 
 To continue the same thread, appending to the last entry:
   journal_update("additional text")