Correct the rekey tick comments to match the retirement phase

The poll_rekey doc still said it reproduced the earlier priority and
phase grouping exactly, and the comment at its call site listed three
phases and described the snapshots as unchanged. The responder hold
added a retirement phase between drains and initiations, and two
snapshot fields, so both comments now describe the four phases as they
are.

src/node/handlers/rekey.rs

@@ -126,13 +126,14 @@ impl Node {
         };
 
         // The shell snapshots each healthy peer's rekey ages/flags (every clock
-        // read resolved here); the core decides cutover/drain/trigger with no
-        // clock, phase-grouped to preserve the pre-refactor execution order.
-        // The batch `poll_rekey` + snapshots STAY SHELL-SIDE and BYTE-UNCHANGED:
-        // the cross-peer phase-grouping (all Cutover → all Drain →
-        // all InitiateRekey) governs the shared `index_allocator` free-then-alloc
-        // SEQUENCE that appears on the wire. The machine must NOT re-poll; it
-        // CONSUMES each decided `ConnAction` in the same order the batch returned.
+        // read resolved here); the core decides cutover, drain, retirement and
+        // trigger with no clock and returns the actions phase-grouped: all
+        // Cutover, then all Drain, then all RetirePending, then all
+        // InitiateRekey. That grouping fixes the shared `index_allocator`
+        // free-then-allocate sequence that appears on the wire, so the batch
+        // `poll_rekey` call stays here in the shell. The machine must NOT
+        // re-poll; it CONSUMES each decided `ConnAction` in the order the batch
+        // returned.
         let snapshots = self.rekey_peers();
         for action in self.fmp.poll_rekey(snapshots, &cfg) {
             match action {

src/proto/fmp/core.rs

@@ -525,8 +525,7 @@ impl Fmp {
     }
 
     /// Decide the per-tick rekey choreography for the healthy peers the shell
-    /// snapshotted. Reproduces the pre-refactor priority and phase grouping
-    /// exactly:
+    /// snapshotted, in this priority:
     ///
     /// - **Cutover** takes precedence: a peer with a pending session this node
     ///   initiated and no in-flight rekey cuts over and is considered for
@@ -538,7 +537,7 @@ impl Fmp {
     ///   trigger fires when the peer is neither mid-rekey, dampened, nor
     ///   holding a pending session, and its jittered time threshold or send
     ///   counter is reached. A draining peer can thus both drain and
-    ///   re-trigger in the same tick, as before.
+    ///   re-trigger in the same tick.
     ///
     /// Actions are returned phase-grouped (all cutovers, then all drains, then
     /// all retirements, then all rekey initiations) to preserve the global