Add Remote controller capture IPC to the host and both SDKs

remote.focus lets a controller keyboard-capture lease ask core to enter
or leave remote focus; the reply acknowledges admission only. Core
reports the actual state with remote.focus events and forwards routed
transitions as remote.input events carrying the source keycode and, on
fresh presses, a canonical key name. A full focus mailbox revokes the
lease; revocation drains pending focus work. No native capture owner is
attached yet.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/tentaclewire/remote_capture_test.go

@@ -0,0 +1,81 @@
+// Copyright (c) 2026 Storm Dragon
+// Authors: Storm Dragon, Angus Kola
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+package tentaclewire
+
+import (
+	"encoding/json"
+	"strings"
+	"testing"
+)
+
+func TestRemoteCapturedKeyValidation(t *testing.T) {
+	for _, key := range []RemoteCapturedKey{
+		{Code: 8, Name: "a", Pressed: true}, {Code: 255, Name: "Shift_R", Pressed: true},
+		{Code: 38, Pressed: true, Repeat: true}, {Code: 38},
+	} {
+		if !ValidRemoteCapturedKey(key) {
+			t.Fatal("valid key rejected", key)
+		}
+		data, _ := json.Marshal(key)
+		var decoded RemoteCapturedKey
+		if json.Unmarshal(data, &decoded) != nil || decoded != key {
+			t.Fatal("round trip changed key", key)
+		}
+	}
+	for _, raw := range []string{
+		`{"code":7,"name":"a","pressed":true}`, `{"code":256,"name":"a","pressed":true}`,
+		`{"code":38,"name":"Prior","pressed":true}`, `{"code":38,"name":"a","pressed":false}`,
+		`{"code":38,"pressed":false,"repeat":true}`, `{"code":38,"pressed":true}`,
+		`{"name":"a","pressed":true}`, `{"code":38,"name":"a"}`,
+		`{"code":38,"name":"a","pressed":true,"origin":"local"}`, `{"code":38,"code":39,"name":"a","pressed":true}`,
+	} {
+		var key RemoteCapturedKey
+		if json.Unmarshal([]byte(raw), &key) == nil {
+			t.Fatal("invalid key decoded", raw)
+		}
+	}
+}
+
+func TestRemoteFocusRequestAndEventValidation(t *testing.T) {
+	lease := strings.Repeat("a", 32)
+	var request RemoteFocusRequest
+	if json.Unmarshal([]byte(`{"lease":"`+lease+`","epoch":1,"sequence":2,"remote":false}`), &request) != nil || request.Remote || request.Sequence != 2 {
+		t.Fatal("valid focus request rejected", request)
+	}
+	for _, raw := range []string{
+		`{"lease":"` + lease + `","epoch":1,"sequence":2}`,
+		`{"lease":"` + lease + `","epoch":1,"sequence":0,"remote":true}`,
+		`{"lease":"short","epoch":1,"sequence":2,"remote":true}`,
+		`{"lease":"` + lease + `","epoch":1,"sequence":2,"remote":"yes"}`,
+	} {
+		if json.Unmarshal([]byte(raw), &request) == nil {
+			t.Fatal("invalid focus request decoded", raw)
+		}
+	}
+	key := RemoteCapturedKey{Code: 38, Name: "a", Pressed: true}
+	valid := []SessionEvent{
+		{Sequence: 1, Epoch: 1, Kind: "remote.input", Lease: lease, Input: &key},
+		{Sequence: 1, Epoch: 1, Kind: "remote.focus", Lease: lease, Focus: "remote", Reason: "requested"},
+		{Sequence: 1, Epoch: 1, Kind: "remote.focus", Lease: lease, Focus: "local", Reason: "escape"},
+	}
+	for _, event := range valid {
+		if !ValidSessionEvent(event) {
+			t.Fatal("valid event rejected", event)
+		}
+	}
+	invalid := []SessionEvent{
+		{Sequence: 1, Epoch: 1, Kind: "remote.input", Lease: lease},
+		{Sequence: 1, Epoch: 1, Kind: "remote.input", Lease: lease, Input: &key, Focus: "remote"},
+		{Sequence: 1, Epoch: 1, Kind: "remote.focus", Lease: lease, Focus: "remote", Reason: "network"},
+		{Sequence: 1, Epoch: 1, Kind: "remote.focus", Lease: lease, Focus: "elsewhere", Reason: "requested"},
+		{Sequence: 1, Epoch: 1, Kind: "remote.revoked", Lease: lease, Reason: "closed", Input: &key},
+		{Sequence: 1, Epoch: 1, Kind: "remote.revoked", Lease: lease, Reason: "closed", Focus: "local"},
+	}
+	for _, event := range invalid {
+		if ValidSessionEvent(event) {
+			t.Fatal("invalid event accepted", event)
+		}
+	}
+}