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.

docs/PLUGINS.md

@@ -1,6 +1,6 @@
 # AgentHub — Plugin Marketplace
 
-Official Claude Code plugins for the Agent Monitor dashboard. The **`agenthub`** plugin _is_ the dashboard — hooks, server and the `agenthub` CLI, no checkout required. (It shipped an MCP server until `c7dbaf2`, which dropped it; the dashboard reads Claude Code's MCP configuration in the config explorer but no longer serves one.) On top of it, **10 focused plugins** extend Claude Code with skills, agents, slash commands, hooks, and CLI tools for deep analytics, cost guardrails, productivity automation, developer tools, AI-powered insights, session forensics, workflow/fleet intelligence, reliability & SLOs, config & memory governance, and dashboard connectivity.
+Official Claude Code plugins for the Agent Monitor dashboard. The **`agenthub`** plugin _is_ the dashboard — hooks, server and the `agenthub` CLI, no checkout required. (It ships a small read-only MCP server again — `agenthub mcp`, see [MCP.md](./MCP.md) — but does not register it: run `claude mcp add agenthub -- agenthub mcp` to opt in. The same goes for the statusline, `agenthub statusline install`, see [STATUSLINE.md](./STATUSLINE.md).) On top of it, **10 focused plugins** extend Claude Code with skills, agents, slash commands, hooks, and CLI tools for deep analytics, cost guardrails, productivity automation, developer tools, AI-powered insights, session forensics, workflow/fleet intelligence, reliability & SLOs, config & memory governance, and dashboard connectivity.
 
 Every plugin is powered by the local Agent Monitor REST API at `http://localhost:4820`. They are read-only advisors unless a skill explicitly documents a mutating endpoint (and those preview + confirm before acting).
 
@@ -632,7 +632,7 @@ These plugins query the Agent Monitor API at `http://localhost:4820`. Key data s
 11 datasets: `stats`, `orchestration` (DAG), `toolFlow` (transitions), `effectiveness` (subagent success), `patterns` (recurring sequences), `modelDelegation`, `errorPropagation` (by depth), `concurrency` (lanes), `complexity` (score), `compaction` (impact), `cooccurrence` (agent pairs)
 
 ### Alert Rules (`/api/alerts/rules`)
-Rule types: `token_threshold` (`{ total_tokens }` — the spend-relevant guardrail), `event_pattern`, `inactivity`, `status_duration`.
+Rule types: `budget` (`{ period: day|week|month, limit_usd, thresholds: [80, 100], tool?, lane?, tz_offset? }` — a spend limit in dollars, each threshold firing once per period; `GET /api/budgets/status` reports the current period), `cost_threshold` (`{ usd }` per session), `token_threshold` (`{ total_tokens }`), `event_pattern`, `inactivity`, `status_duration`. `POST /api/alerts/rules/preview` dry-runs any of them over recorded history.
 
 ### Config Explorer (`/api/cc-config/*`)
 Read every Claude Code surface (skills, agents, commands, output-styles, plugins, marketplaces, mcp, hooks, settings, keybindings, statusline, memory). A plugin card's contribution chips are clickable: each one expands to name the skills / subagents / commands / output styles that plugin ships (from `contributes.items`), so the plugin's contents are readable without opening its install directory. `memory` includes the per-project file-based store with `scope: "auto-memory"` (carrying `project`, `name`, `isIndex`, `frontmatter`); those files plus `CLAUDE.md` are mutable via `PUT`/`DELETE /api/cc-config/file` with always-on timestamped backups. The page also **manages plugins and marketplaces**: paste a GitHub `owner/repo`, URL or local path to register a marketplace, then install / enable / disable / update / uninstall its plugins — each button runs the corresponding `claude plugin …` command on the dashboard host (argv array, never a shell string). Hooks and `settings.json` keys are editable per layer (user / project / project-local) through `PATCH /api/cc-config/settings`, a per-key merge that leaves every untouched key — including redacted secrets — exactly as it was.