feat: per-tool settings, persistent settings file, Codex and Antigravity sessions, tokens and hooks (#40 B, C1, C2, D)

Part B: Model Pricing, Hook Configuration and CLAUDE_HOME move from
Settings → Dashboard to the Claude Code tab's AgentHub sub-tab
(ClaudeAgentHubSettings.tsx); CODEX_HOME is editable in Codex → AgentHub.
A home that is or contains the OS home is refused (EBADHOME).

Settings persistence: dashboard-saved settings go to
~/.config/agenthub/settings.env (AGENTHUB_SETTINGS_FILE), outside the plugin
cache an update wipes. Load order: real env > the checkout's .env > that file.
The first CLAUDE_HOME change pins DASHBOARD_DATA_DIR so the DB stays put.

C1: codex-usage.js reads Codex rollout journals into sessions (new column
tool) and token_usage, tracked per file in codex_rollouts; forks deduped by
total vector, sub-agent threads folded into the root; pricing-sync also
prices OpenAI models; PricingSettings with a vendor filter.

C2: codex-hooks.js installs AgentHub's hooks into $CODEX_HOME/hooks.json on
a click, through a stable forwarder; Codex trust is never written. The hook
route creates tool='codex' sessions and folds sub-agent hooks into the root.

D: antigravity-usage.js reads agy's per-conversation SQLite files (tokens
from ModelUsageStats) into tool='antigravity' sessions; antigravity-hooks.js
installs the named hook `agenthub` (PreInvocation, PostToolUse, Stop — never
PreToolUse) into ~/.gemini/config/hooks.json; Settings → Antigravity tab;
Gemini pricing.

Whole-change review fixes: sameOriginGuard on both home PUTs, routers.missing
on a CLAUDE_HOME change, reset-pricing scope, GET /api/sessions?tool=,
clear-data covering the new tables, Codex child-thread events moving no
status, hooks owning status only while current, EFOREIGN for a forwarder
that is not ours, agy quiet window and turn rules, AGENTHUB_SETTINGS_FILE
honoured from .env.

Docs, OpenAPI and the CLAUDE.md marker updated. Server 2141, client 779.

client/src/pages/SessionDetail.tsx

@@ -85,6 +85,7 @@ import { AgentCard } from "../components/AgentCard";
 import { SessionOverview } from "../components/SessionOverview";
 import { ConversationView } from "../components/conversation/ConversationView";
 import { SessionStatusBadge, AgentStatusBadge, REASON_ICONS } from "../components/StatusBadge";
+import { SessionToolBadge } from "../components/SessionToolBadge";
 import { CopyButton } from "../components/event-views/primitives";
 import {
   effectiveSessionStatus,
@@ -589,6 +590,7 @@ export function SessionDetail() {
             <h2 className="text-xl font-semibold text-fg-primary">
               {session.name || `${t("defaultName")}${session.id.slice(0, 8)}`}
             </h2>
+            <SessionToolBadge tool={session.tool} />
             <SessionStatusBadge
               status={effectiveSessionStatus(session)}
               reason={sessionAwaitingReason(session)}