feat: analytics parity — tool cost, date ranges, budgets, query explorer, replay, snapshots (v2.4.0)

Analytics parity phases 2–7 (docs/plans/analytics-parity/), built on
138e706 and ported onto v2.3.1:
- Cost by AI tool (?tool= on cost/analytics/stats/workflows, by_tool,
  Codex fast/priority and flex tiers, agenthub_cost_usd_total{tool,model})
- Date ranges (from/to) on cost/analytics/workflows; Analytics range select
  with Today / This week (Monday) / This month (1st) / 7d / 30d / 90d / All /
  Custom; workflow filters carried into workflow-stats.js (read worker)
- Budgets and cost alerts as alert rule types (alert_rules rebuilt without
  its rule_type CHECK), GET /api/budgets/status, rule preview, spend pace,
  status-bar budget chip; rules stay editable in place
- Query Explorer (/query, allowlisted sort, CSV/JSON export) and scheduled
  reports (report_definitions/report_runs, Settings → Reports)
- Session Replay tab and immutable snapshots (session_snapshots, /snapshot/:token)
- Remote Codex sync, push ingest with a hashed token, privacy redaction and
  ignored folders (Settings → Data), Cursor sessions (no cost)
- Read-only MCP server, statusline, Grafana/Prometheus files

Also: resizable sidebar, pet run/wave animations, the workspace home keeps a
half-typed prompt, and the pre-commit hook runs only the related tests for a
small commit.

client/src/i18n/locales/en/alerts.json

@@ -7,20 +7,26 @@
     "event_pattern": "Event pattern",
     "inactivity": "Inactivity",
     "status_duration": "Stuck agent",
-    "token_threshold": "Token threshold"
+    "token_threshold": "Token threshold",
+    "cost_threshold": "Cost threshold",
+    "budget": "Spend budget"
   },
   "ruleTypeHints": {
     "event_pattern": "Fires when an ingested event matches the pattern. Set a count above 1 to require N matching events within a time window (e.g. more than 5 errors in 2 minutes).",
     "inactivity": "Fires when an active session has received no events for the configured number of minutes.",
     "status_duration": "Fires when an agent has remained in the selected status with no activity for the configured number of minutes.",
-    "token_threshold": "Fires when a session's total token usage (input + output + cache) exceeds the threshold."
+    "token_threshold": "Fires when a session's total token usage (input + output + cache) exceeds the threshold.",
+    "cost_threshold": "Fires when a session's cost reaches the amount, priced like the session's own cost.",
+    "budget": "Fires once per period at each threshold of a spend limit — per day, week or month in your local time, optionally for one AI tool."
   },
   "ruleDesc": {
     "eventPattern": "Matches {{pattern}}",
     "eventPatternCount": "≥{{count}} × {{pattern}} within {{window}} min",
     "inactivity": "No session activity for {{minutes}} min",
     "statusDuration": "Agent stuck in {{status}} for {{minutes}} min",
-    "tokenThreshold": "Session tokens exceed {{tokens}}"
+    "tokenThreshold": "Session tokens exceed {{tokens}}",
+    "costThreshold": "Session cost reaches {{usd}}",
+    "budget": "{{limit}} per {{period}} · alerts at {{thresholds}}"
   },
   "rules": {
     "title": "Alert rules",
@@ -48,7 +54,13 @@
       "agentStatus": "Agent status",
       "minutes": "Minutes",
       "totalTokens": "Total tokens",
-      "cooldown": "Cooldown (seconds)"
+      "cooldown": "Cooldown (seconds)",
+      "usd": "Cost (USD)",
+      "period": "Period",
+      "limitUsd": "Limit (USD)",
+      "thresholds": "Alert at (%)",
+      "budgetTool": "AI tool",
+      "allTools": "All AI tools"
     },
     "deleteTitle": "Delete alert rule?",
     "help": {
@@ -63,8 +75,19 @@
       "minutesInactivity": "Fire when an active session has had no events for this many minutes (a stalled or forgotten session).",
       "minutesStatus": "Fire when an agent stays in the selected status with no activity for this many minutes (a stuck agent).",
       "totalTokens": "Fire when a session's cumulative tokens (input + output + cache read + cache write) cross this number. e.g. 1000000 = 1M tokens.",
-      "cooldown": "Minimum seconds between repeat alerts for the same rule + session + agent. Prevents noisy duplicates. Default 300 (5 min); 0 = no cooldown."
+      "cooldown": "Minimum seconds between repeat alerts for the same rule + session + agent. Prevents noisy duplicates. Default 300 (5 min); 0 = no cooldown.",
+      "usd": "A session reaching this many US dollars fires the alert.",
+      "period": "Day starts at your local midnight, week on Monday, month on the 1st.",
+      "limitUsd": "The spend limit for one period, in US dollars.",
+      "thresholds": "Percents of the limit, comma-separated, e.g. 50, 80, 100. Each fires once per period.",
+      "budgetTool": "Count only this AI tool's sessions."
     },
+    "preview": "Preview",
+    "previewing": "Checking…",
+    "previewHint": "What this rule would have fired over the last 7 days — nothing is saved or sent",
+    "previewResult": "Would have fired {{fires}} times in {{sessions}} sessions over the last {{days}} days.",
+    "previewBudget": "Spend per period (this one and the five before it):",
+    "previewUnsupported": "This rule type cannot be replayed from history.",
     "edit": "Edit rule",
     "save": "Save rule",
     "typeFixed": "A rule's type cannot be changed — create a new rule instead.",
@@ -81,6 +104,11 @@
     "emptyDescription": "Alerts fired by your rules will appear here in real time.",
     "emptyUnacked": "Everything is acknowledged. New alerts will appear here as they fire."
   },
+  "periods": {
+    "day": "day",
+    "week": "week",
+    "month": "month"
+  },
   "errors": {
     "loadRules": "Could not load alert rules: {{error}}",
     "loadAlerts": "Could not load alerts: {{error}}",