feat: add antigravity-cli integration (#2087)

* feat: add antigravity_cli integration harness

Register the `antigravity_cli` target, resolve its configuration
directory to `~/.gemini/antigravity-cli/`, wire target actions,
and add lifecycle hook scripts for Unix and Windows.

* feat: support session resume for antigravity-cli

* fix: correct antigravity-cli hook config path, shape, and agent label

Antigravity CLI reads global customizations from ~/.gemini/config, keys
hooks.json by hook name, and only accepts the matcher/hooks wrapper for
the tool events. The previous install wrote event arrays at the top level
of ~/.gemini/antigravity-cli/hooks.json, which agy never reads and would
reject anyway, so no Herdr hook ever ran.

Session reports were dropped for a third reason: the hooks reported the
agent as antigravity-cli, but the server normalizes that to the canonical
label agy before matching, so is_official_agent_source never matched and
agy --conversation resume was unreachable.

- Resolve the config dir to ~/.gemini/config
- Nest Herdr entries under a Herdr-owned "herdr" block that install
  rewrites and uninstall removes, leaving other named hooks untouched
- Emit grouped entries for PreToolUse/PostToolUse and flat handler lists
  for PreInvocation/PostInvocation/Stop
- Report the canonical agy label from both hook assets and match it in
  agent_resume
- Compile-gate the hook asset constants and stop shadowing $args in the
  PowerShell hook
- Document the real directory, that it must already exist, and the
  named-block behavior

refs #1011
refs #1571

* fix: make antigravity-cli integration session-only

antigravity cli cannot express lifecycle safely: there is no blocked
event, postinvocation is skipped on interruption, and stop fires at the
end of a turn rather than on process exit, which left stale state and
released authority at the wrong time.

report only the conversation on preinvocation and let screen detection
own agent state. resume via `agy --conversation <id>` is unchanged.

* fix: update antigravity session after conversation switch

---------

Co-authored-by: Can Celik <ogulcancelik@gmail.com>

2 files changed, 134 insertions, 0 deletions

diff --git a/src/integration/assets/antigravity_cli/herdr-agent-state.ps1 b/src/integration/assets/antigravity_cli/herdr-agent-state.ps1
new file mode 100644
index 00000000..aecb42a9
--- /dev/null
+++ b/src/integration/assets/antigravity_cli/herdr-agent-state.ps1
@@ -0,0 +1,57 @@
+# installed by herdr
+# managed by herdr; reinstalling or updating the integration overwrites this file.
+# add custom hooks beside this file instead of editing it.
+# HERDR_INTEGRATION_ID=antigravity_cli
+# HERDR_INTEGRATION_VERSION=1
+
+# Session-only: this hook reports the Antigravity conversation so Herdr can
+# resume the pane. Lifecycle state comes from Herdr's screen detection.
+
+param([string]$Action = "")
+
+# Antigravity CLI expects a JSON object on stdout and this hook never injects
+# anything, so every exit path emits an empty object.
+function Exit-Hook {
+    Write-Output "{}"
+    exit 0
+}
+
+if ($Action -ne "session") { Exit-Hook }
+if ($env:HERDR_ENV -ne "1") { Exit-Hook }
+if ([string]::IsNullOrWhiteSpace($env:HERDR_PANE_ID)) { Exit-Hook }
+
+$inputText = [Console]::In.ReadToEnd()
+try {
+    $payload = if ([string]::IsNullOrWhiteSpace($inputText)) { $null } else { $inputText | ConvertFrom-Json }
+} catch {
+    Exit-Hook
+}
+
+if ($null -eq $payload) { Exit-Hook }
+
+$conversationId = if ($payload.conversationId -is [string]) { $payload.conversationId } else { $null }
+if ([string]::IsNullOrWhiteSpace($conversationId)) { Exit-Hook }
+
+$seq = [DateTimeOffset]::UtcNow.ToUnixTimeMilliseconds()
+try {
+    $sessionArgs = @(
+        "pane",
+        "report-agent-session",
+        $env:HERDR_PANE_ID,
+        "--source",
+        "herdr:antigravity_cli",
+        "--agent",
+        "agy",
+        "--seq",
+        "$seq",
+        "--agent-session-id",
+        "$conversationId"
+    )
+    if ($payload.transcriptPath -is [string] -and -not [string]::IsNullOrWhiteSpace($payload.transcriptPath)) {
+        $sessionArgs += @("--agent-session-path", "$($payload.transcriptPath)")
+    }
+    & herdr @sessionArgs 2>$null | Out-Null
+} catch {
+}
+
+Exit-Hook
diff --git a/src/integration/assets/antigravity_cli/herdr-agent-state.sh b/src/integration/assets/antigravity_cli/herdr-agent-state.sh
new file mode 100644
index 00000000..dd3db028
--- /dev/null
+++ b/src/integration/assets/antigravity_cli/herdr-agent-state.sh
@@ -0,0 +1,77 @@
+#!/bin/sh
+# installed by herdr
+# managed by herdr; reinstalling or updating the integration overwrites this file.
+# add custom hooks beside this file instead of editing it.
+# HERDR_INTEGRATION_ID=antigravity_cli
+# HERDR_INTEGRATION_VERSION=1
+
+# Session-only: this hook reports the Antigravity conversation so Herdr can
+# resume the pane. Lifecycle state comes from Herdr's screen detection.
+
+set -eu
+
+# Antigravity CLI expects a JSON object on stdout and this hook never injects
+# anything, so every exit path emits an empty object.
+emit_and_exit() {
+  printf '{}\n'
+  exit 0
+}
+
+[ "${1:-}" = "session" ] || emit_and_exit
+[ "${HERDR_ENV:-}" = "1" ] || emit_and_exit
+[ -n "${HERDR_SOCKET_PATH:-}" ] || emit_and_exit
+[ -n "${HERDR_PANE_ID:-}" ] || emit_and_exit
+command -v python3 >/dev/null 2>&1 || emit_and_exit
+
+python3 -c '
+import json
+import os
+import socket
+import sys
+import time
+
+try:
+    payload = json.load(sys.stdin)
+except Exception:
+    raise SystemExit(0)
+
+if not isinstance(payload, dict):
+    raise SystemExit(0)
+
+def text(name):
+    value = payload.get(name)
+    return value if isinstance(value, str) and value else None
+
+session_id = text("conversationId")
+if session_id is None:
+    raise SystemExit(0)
+
+seq = time.time_ns()
+params = {
+    "pane_id": os.environ["HERDR_PANE_ID"],
+    "source": "herdr:antigravity_cli",
+    "agent": "agy",
+    "seq": seq,
+    "agent_session_id": session_id,
+}
+
+transcript_path = text("transcriptPath")
+if transcript_path is not None:
+    params["agent_session_path"] = transcript_path
+
+request = json.dumps({
+    "id": f"herdr:antigravity_cli:{seq}",
+    "method": "pane.report_agent_session",
+    "params": params,
+})
+try:
+    with socket.socket(socket.AF_UNIX, socket.SOCK_STREAM) as client:
+        client.settimeout(0.5)
+        client.connect(os.environ["HERDR_SOCKET_PATH"])
+        client.sendall((request + "\n").encode())
+        client.recv(4096)
+except Exception:
+    pass
+' 2>/dev/null || true
+
+emit_and_exit