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.

.env.example

@@ -2,6 +2,11 @@
 # Override this if your Claude Code data is in a different location, e.g.:
 #   CLAUDE_HOME=~/.codefuse/engine/cc
 # CLAUDE_HOME=~/.claude
+# A value saved from Settings (CLAUDE_HOME, CODEX_HOME, a pinned DASHBOARD_DATA_DIR)
+# goes to ~/.config/agenthub/settings.env (AGENTHUB_SETTINGS_FILE). This file wins
+# over it, and the real environment wins over both; a key set here or in the real
+# environment is reported as env-owned in Settings (a value saved there would be
+# overridden again at the next start).
 
 # ── Server / network ────────────────────────────────────────────────────────
 # Port to listen on (default: 4820)
@@ -66,6 +71,27 @@
 # Set to 0 to disable the poll while leaving the watcher running (default: 30000).
 #   DASHBOARD_SESSION_SYNC_MS=30000
 
+# Poll interval (ms) for Antigravity CLI sessions and tokens, read from agy's
+# own ~/.gemini/antigravity-cli/conversations/*.db (0 disables; default: 15000).
+#   DASHBOARD_ANTIGRAVITY_POLL_MS=15000
+# Where agy keeps its data, when not ~/.gemini (agy itself has no override).
+#   AGENTHUB_GEMINI_DIR=~/.gemini
+
+# Poll interval (ms) for Codex's rollout journals ($CODEX_HOME/sessions/**):
+# drives both the codex lane running/idle mirror and Codex sessions + tokens
+# (0 disables both; default: 15000).
+#   DASHBOARD_CODEX_POLL_MS=15000
+
+# Automatic pricing: a model seen in token usage with no rate row of its own
+# gets one from LiteLLM's public price list. 0 / false / off disables it
+# (default: enabled).
+#   AGENTHUB_PRICING_SYNC=0
+
+# Where settings saved from the dashboard persist (default:
+# $XDG_CONFIG_HOME/agenthub/settings.env, i.e. ~/.config/agenthub/settings.env).
+# Here or in the real environment; the file is located after this one loads.
+#   AGENTHUB_SETTINGS_FILE=/home/you/.config/agenthub/settings.env
+
 # ── Remote Data Sources (SSH multi-machine collection) ───────────────────────
 # The dashboard can pull Claude Code history from other machines over SSH:
 # it rsyncs each enabled remote's ~/.claude/projects into a sandboxed staging