mcp: add mcp-schema command for generic MCP bridge

Add `poc-memory mcp-schema` command that outputs tool definitions with
CLI routing info (name, description, inputSchema, cli args, stdin_param).

The companion memory-mcp.py (in ~/bin/) is a generic bridge that loads
definitions from mcp-schema at startup and dynamically generates typed
Python functions for FastMCP registration. No tool-specific Python code
— adding a new tool only requires changes in Rust.

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

src/main.rs

@@ -220,6 +220,10 @@ EXAMPLES:
     /// Admin operations (fsck, health, import, export)
     #[command(subcommand)]
     Admin(AdminCmd),
+
+    /// Output MCP tool definitions as JSON (for generic MCP bridge)
+    #[command(name = "mcp-schema")]
+    McpSchema,
 }
 
 #[derive(Subcommand)]
@@ -310,6 +314,14 @@ enum GraphCmd {
         /// Node key
         key: Vec<String>,
     },
+    /// Find related nodes via spreading activation from seed nodes
+    Spread {
+        /// Seed node keys
+        keys: Vec<String>,
+        /// Maximum results (default: 20)
+        #[arg(short = 'n', default_value_t = 20)]
+        max_results: usize,
+    },
     /// Add a link between two nodes
     #[command(name = "link-add")]
     LinkAdd {
@@ -806,6 +818,7 @@ impl Run for Command {
             Self::Cursor(sub)            => sub.run(),
             Self::Agent(sub)             => sub.run(),
             Self::Admin(sub)             => sub.run(),
+            Self::McpSchema              => cli::misc::cmd_mcp_schema(),
         }
     }
 }
@@ -837,6 +850,7 @@ impl Run for GraphCmd {
     fn run(self) -> Result<(), String> {
         match self {
             Self::Link { key }                  => cli::graph::cmd_link(&key),
+            Self::Spread { keys, max_results }  => cli::graph::cmd_spread(&keys, max_results),
             Self::LinkAdd { source, target, reason }
                 => cli::graph::cmd_link_add(&source, &target, &reason),
             Self::LinkSet { source, target, strength }