fix(automations): sub-second awaiting-agent keys and discard stale processing rows on edit

- awaiting_agent episode keys use sub-second (.to_f) precision like status keys,
  so a reply then re-wait within the same second is a distinct episode and the
  original armed row no longer matches the later waiting period.
- discard_stale_pending_executions now deletes armed rows (pending and stale
  processing), since the sweep reclaims stale processing rows and would otherwise
  fire them against the edited rule definition.

app/models/automation_rule.rb

@@ -133,7 +133,8 @@ class AutomationRule < ApplicationRecord
   end
 
   def discard_stale_pending_executions
-    pending_executions.pending.delete_all
+    # Includes stale processing rows: the sweep would otherwise reclaim and fire them.
+    pending_executions.armed.delete_all
   end
 
   def validate_single_condition(condition)

app/models/automation_rule_pending_execution.rb

@@ -42,6 +42,9 @@ class AutomationRulePendingExecution < ApplicationRecord
     pending.where(due_at: ..Time.current).or(processing.where(updated_at: ...STALE_PROCESSING_TIMEOUT.ago))
   }
 
+  # Non-terminal rows still bound to fire (a stale processing row is reclaimed by the sweep).
+  scope :armed, -> { where(status: [statuses[:pending], statuses[:processing]]) }
+
   def self.schedule(rule:, conversation:, message: nil)
     key = arm_episode_key_for(conversation, message)
     create!(
@@ -63,7 +66,7 @@ class AutomationRulePendingExecution < ApplicationRecord
   def self.arm_episode_key_for(conversation, message)
     return episode_key_for(conversation, message) unless message&.incoming? && conversation.waiting_since.blank?
 
-    "awaiting_agent:#{message.created_at.to_i}"
+    "awaiting_agent:#{message.created_at.to_f}"
   end
 
   # Episode keys identify one qualifying stretch of conversation state; when the recomputed
@@ -73,9 +76,10 @@ class AutomationRulePendingExecution < ApplicationRecord
       # Sub-second precision so a resolve→reopen inside one second still ends the episode.
       "status:#{(conversation.status_changed_at.presence || conversation.created_at).to_f}"
     elsif message.incoming?
-      # waiting_since is cleared on agent/bot reply, so a reply invalidates this episode.
-      # Strict here: at fire time a nil waiting_since means the agent replied (episode ended).
-      "awaiting_agent:#{conversation.waiting_since.to_i}"
+      # waiting_since is cleared on agent/bot reply, so a reply invalidates this episode. Strict
+      # here: at fire time a nil waiting_since means the agent replied (episode ended). Sub-second
+      # precision so a reply→re-wait inside one second is still a distinct episode.
+      "awaiting_agent:#{conversation.waiting_since.to_f}"
     else
       # A new customer message changes the max incoming id, invalidating this episode.
       "reply_chase:#{conversation.messages.incoming.maximum(:id) || 0}"