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.

server/lib/codex-home.js

@@ -2,10 +2,12 @@
  * @file Centralized Codex home directory path management. Resolves the Codex
  * home directory, project-level Codex surfaces, and project roots. Supports a
  * custom root via the CODEX_HOME environment variable so the dashboard can
- * track non-standard Codex installations.
+ * track non-standard Codex installations, and changes it at runtime
+ * (`setCodexHome`, persisted to the settings file).
  * @author Nguyễn Ngọc Trí Vĩ <vinnt@smartgift.vn>
  */
 
+const fs = require("node:fs");
 const path = require("node:path");
 const os = require("node:os");
 
@@ -19,6 +21,22 @@ function getCodexHome() {
   return process.env.CODEX_HOME || path.join(os.homedir(), ".codex");
 }
 
+/**
+ * CODEX_HOME as given and, when a symlink makes it differ, as resolved — so a
+ * path Codex reports (it may canonicalize) matches either.
+ *
+ * @returns {string[]} one or two absolute paths.
+ */
+function codexHomes() {
+  const raw = path.resolve(getCodexHome());
+  try {
+    const real = fs.realpathSync(raw);
+    return real === raw ? [raw] : [raw, real];
+  } catch {
+    return [raw];
+  }
+}
+
 /**
  * The directory where Codex stores per-project surfaces (rollout journals,
  * SQLite mirrors, etc.) for a project at the given working directory.
@@ -42,8 +60,27 @@ function getProjectRoot(cwd) {
   return cwd;
 }
 
+/**
+ * Update CODEX_HOME at runtime: `process.env` changes at once and the value
+ * persists to the settings file (see `settings-env.js`). The path passes the
+ * shared guard that refuses anything that is or contains the user's home
+ * (`EBADHOME`). A codex pane gets this value through tmux `-e` at its next
+ * start; one already running keeps the home it started with.
+ *
+ * @param {string} newPath absolute path, `~/` expanded.
+ * @returns {string} the resolved absolute path.
+ */
+function setCodexHome(newPath) {
+  const { validateHomeDir, applySetting } = require("./settings-env");
+  const resolved = validateHomeDir("CODEX_HOME", newPath);
+  applySetting("CODEX_HOME", resolved);
+  return resolved;
+}
+
 module.exports = {
+  codexHomes,
   getCodexHome,
+  setCodexHome,
   getProjectCodexDir,
   getProjectRoot,
 };