journal tools: use NodeType instead of string key matching

- journal_new: create EpisodicSession node with auto-generated key
- journal_tail: query by node_type, not by parsing a monolithic node
- journal_update: find latest EpisodicSession by timestamp
- No string key matching anywhere — all typed
- Fixes journal entries not appearing in 'poc-memory journal tail'
- Also: added --provenance/-p filter to 'poc-memory tail'
- Also: fix early return in surface_observe_cycle store load failure
- Also: scale max_turns by number of steps (50 per step)

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

src/main.rs

@@ -90,6 +90,9 @@ enum Command {
         /// Show full content
         #[arg(long)]
         full: bool,
+        /// Filter by provenance (substring match, e.g. "surface-observe")
+        #[arg(long, short)]
+        provenance: Option<String>,
     },
     /// Summary of memory state
     Status,
@@ -782,7 +785,8 @@ impl Run for Command {
             Self::Write { key }         => cli::node::cmd_write(&key),
             Self::Edit { key }          => cli::node::cmd_edit(&key),
             Self::History { full, key }  => cli::node::cmd_history(&key, full),
-            Self::Tail { n, full }       => cli::journal::cmd_tail(n, full),
+            Self::Tail { n, full, provenance }
+                => cli::journal::cmd_tail(n, full, provenance.as_deref()),
             Self::Status                 => cli::misc::cmd_status(),
             Self::Query { expr }         => cli::misc::cmd_query(&expr),
             Self::Used { key }           => cli::node::cmd_used(&key),