fix(rust): send reward notices, and keep a downed line's credit rule (W21, W4)

W21: the permission push named its fields one by one and left out
`notices`, so no kit reward, lend or give ever told its player
anything (D333). The body is now built by `pushBody`, which carries
every field the payload has; a test fails if a payload field is
dropped again.

W4: a downed patrol helicopter, Chinook or Bradley is stored with the
credit rule in force when it arrived, and the feed reads that stamp.
Before, the line re-credited past rows with the server's current rule
while the Rotorbane/Tankbreaker counts kept the old one. Rows stored
before this change keep today's reading.

PLAN_LAST_FIXES.md stage 1.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01E14m6SuuY6i1vASFeGDBeY

server/worldEvents.js

@@ -178,7 +178,8 @@ function columnName(index) {
  * `staff`    the viewer is an admin or a moderator: Steam ids, and a type this
  *            build does not know
  * `presence` the viewer is in the server's presence audience: names
- * `rule`     the server's credit rule
+ * `rule`     the server's credit rule, for a row stored before the frame
+ *            carried its own (`stampRule`)
  * `geometry` the server's map geometry, for the grid
  *
  * What comes back keeps the plugin's own fields for what it describes (`event`,
@@ -215,8 +216,8 @@ function shapeFor(frame, { staff = false, presence = false, rule = DEFAULT_CREDI
 
   // Credit, by the server's rule.
   if (known && TYPES[event].credit) {
-    out.creditRule = creditRuleOf(rule)
-    const ids = credited(frame, rule)
+    out.creditRule = ruleOf(frame, rule)
+    const ids = credited(frame, out.creditRule)
     out.creditedCount = ids.length
     if (presence || staff) {
       out.credited = ids.map((id) => ({
@@ -235,6 +236,25 @@ function shapeFor(frame, { staff = false, presence = false, rule = DEFAULT_CREDI
   return out
 }
 
+/**
+ * The frame as it is stored: a downed helicopter, Chinook or Bradley carries
+ * the rule that credited it when it arrived (`creditRule`), so the feed line
+ * keeps naming who the counts were given to after the server's rule changes
+ * (W4). Every other frame is stored as sent.
+ */
+function stampRule(frame, rule) {
+  if (!frame || frame.kind !== 'world.event' || !isKnownType(frame.event) || !TYPES[frame.event].credit) return frame
+  return { ...frame, creditRule: creditRuleOf(rule) }
+}
+
+/**
+ * The rule a stored line is read by: its own stamp, or — for a row from before
+ * the stamp — the server's rule now, which is how those rows always read.
+ */
+function ruleOf(frame, rule) {
+  return frame && CREDIT_RULE_IDS.includes(frame.creditRule) ? frame.creditRule : creditRuleOf(rule)
+}
+
 /**
  * What one `world.event` adds to the counts: a credited kill of a helicopter,
  * a Chinook or a Bradley, for each player the server's rule names. `[{ steamId,
@@ -270,6 +290,8 @@ module.exports = {
   creditRuleOf,
   isKnownType,
   credited,
+  stampRule,
+  ruleOf,
   nameOf,
   gridOf,
   shapeFor,