cursor: spatial memory navigation

Persistent cursor into the knowledge graph with navigation:
- temporal: forward/back among same-type nodes by timestamp
- hierarchical: up/down the digest tree (journal→daily→weekly→monthly)
- spatial: graph neighbor display at every position

The cursor file (~/.claude/memory/cursor) holds a single node key.
Show displays: temporal arrows, hierarchy links, semantic neighbors,
and full content. Date extraction from both timestamps and key names
handles the mixed-timestamp data gracefully.

This is the start of place cells — spatial awareness of position
in your own knowledge.

poc-memory/src/main.rs

@@ -199,6 +199,12 @@ EXAMPLES:
     #[command(subcommand, name = "graph")]
     GraphCmd(GraphCmd),
 
+    // ── Cursor (spatial memory) ──────────────────────────────────────
+
+    /// Navigate the memory graph with a persistent cursor
+    #[command(subcommand)]
+    Cursor(CursorCmd),
+
     // ── Agents ────────────────────────────────────────────────────────
 
     /// Agent and daemon operations
@@ -239,6 +245,27 @@ enum NodeCmd {
     Dump,
 }
 
+#[derive(Subcommand)]
+enum CursorCmd {
+    /// Show current cursor position with context
+    Show,
+    /// Set cursor to a node key
+    Set {
+        /// Node key
+        key: Vec<String>,
+    },
+    /// Move cursor forward in time
+    Forward,
+    /// Move cursor backward in time
+    Back,
+    /// Move up the digest hierarchy (journal→daily→weekly→monthly)
+    Up,
+    /// Move down the digest hierarchy (to first child)
+    Down,
+    /// Clear the cursor
+    Clear,
+}
+
 #[derive(Subcommand)]
 enum JournalCmd {
     /// Write a journal entry to the store
@@ -730,6 +757,9 @@ fn main() {
                 => cmd_organize(&term, threshold, key_only, anchor),
         },
 
+        // Cursor
+        Command::Cursor(sub) => cmd_cursor(sub),
+
         // Agent
         Command::Agent(sub) => match sub {
             AgentCmd::Daemon(sub) => cmd_daemon(sub),
@@ -2167,6 +2197,45 @@ fn cmd_load_context(stats: bool) -> Result<(), String> {
     Ok(())
 }
 
+fn cmd_cursor(sub: CursorCmd) -> Result<(), String> {
+    match sub {
+        CursorCmd::Show => {
+            let store = store::Store::load()?;
+            cursor::show(&store)
+        }
+        CursorCmd::Set { key } => {
+            if key.is_empty() {
+                return Err("cursor set requires a key".into());
+            }
+            let key = key.join(" ");
+            let store = store::Store::load()?;
+            let bare = store::strip_md_suffix(&key);
+            if !store.nodes.contains_key(&bare) {
+                return Err(format!("Node not found: {}", bare));
+            }
+            cursor::set(&bare)?;
+            cursor::show(&store)
+        }
+        CursorCmd::Forward => {
+            let store = store::Store::load()?;
+            cursor::move_temporal(&store, true)
+        }
+        CursorCmd::Back => {
+            let store = store::Store::load()?;
+            cursor::move_temporal(&store, false)
+        }
+        CursorCmd::Up => {
+            let store = store::Store::load()?;
+            cursor::move_up(&store)
+        }
+        CursorCmd::Down => {
+            let store = store::Store::load()?;
+            cursor::move_down(&store)
+        }
+        CursorCmd::Clear => cursor::clear(),
+    }
+}
+
 fn cmd_render(key: &[String]) -> Result<(), String> {
     if key.is_empty() {
         return Err("render requires a key".into());