remove legacy feedback commands (used, wrong, gap, etc.)

These were early experiments with manual feedback signals that
never worked well. The scoring system will handle this properly.

Removed:
- CLI: used, wrong, not-relevant, not-useful, gap
- MCP: memory_used
- Store: mark_used, mark_wrong, record_gap, modify_node

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

src/main.rs

@@ -149,30 +149,6 @@ EXAMPLES:
         /// Query expression (e.g. "key ~ 'inner-life'")
         expr: Vec<String>,
     },
-    /// Mark a memory as useful (boosts weight)
-    Used {
-        /// Node key
-        key: Vec<String>,
-    },
-    /// Mark a memory as wrong/irrelevant
-    Wrong {
-        /// Node key
-        key: String,
-        /// Optional context
-        context: Vec<String>,
-    },
-    /// Mark a search result as not relevant (weakens edges that led to it)
-    #[command(name = "not-relevant")]
-    NotRelevant {
-        /// Node key that was not relevant
-        key: String,
-    },
-    /// Mark a node as not useful (weakens node weight, not edges)
-    #[command(name = "not-useful")]
-    NotUseful {
-        /// Node key
-        key: String,
-    },
     /// Set a node's weight directly
     #[command(name = "weight-set")]
     WeightSet {
@@ -181,11 +157,6 @@ EXAMPLES:
         /// Weight (0.01 to 1.0)
         weight: f32,
     },
-    /// Record a gap in memory coverage
-    Gap {
-        /// Gap description
-        description: Vec<String>,
-    },
 
     // ── Node operations ───────────────────────────────────────────────
 
@@ -523,12 +494,7 @@ impl Run for Command {
                 => cli::journal::cmd_tail(n, full, provenance.as_deref(), !all_versions),
             Self::Status                 => cli::misc::cmd_status(),
             Self::Query { expr }         => cli::misc::cmd_query(&expr),
-            Self::Used { key }           => cli::node::cmd_used(&key),
-            Self::Wrong { key, context } => cli::node::cmd_wrong(&key, &context),
-            Self::NotRelevant { key }    => cli::node::cmd_not_relevant(&key),
-            Self::NotUseful { key }      => cli::node::cmd_not_useful(&key),
             Self::WeightSet { key, weight } => cli::node::cmd_weight_set(&key, weight),
-            Self::Gap { description }    => cli::node::cmd_gap(&description),
             Self::Node(sub)              => sub.run(),
             Self::Journal(sub)           => sub.run(),
             Self::GraphCmd(sub)          => sub.run(),