[chore](dev): keep one Delve server across hot reloads

Replace Air's kill-and-rerun loop in the debug image with the pilot
persistent-delve supervisor: src/dev/dlv-watch.sh owns one headless
`dlv exec --multiclient --continue` server, rebuilds ./tmp/main on save and
restarts only the debug target through the tiny rpc2 client in
src/dev/dlv-restart. An attached VS Code session (and its breakpoints) now
survives saves instead of reconnecting after every reload.

The debug compose builds locally with `pull_policy: build` and without
`build.network: host`: compose cannot grant the network.host entitlement, so
a cold `up` previously failed with "additional privileges requested"; the
default bridge reaches the dev Gitea for module resolution.

src/dev/dlv-restart/main.go

@@ -0,0 +1,62 @@
+// Copyright (C) 2026 Dcntrlized
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published
+// by the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+// dlv-restart is a minimal JSON-RPC client (delve service/rpc2) that restarts
+// the debug target of a persistent headless dlv server and resumes it.
+//
+// Why not `printf 'restart\n' | dlv connect ...`? `dlv connect` is an
+// interactive terminal client: its stdout/stderr is distinct from the debug
+// target's, it always reads go-ahead from the same stream, and its stdin EOF
+// makes it drop into the (dlv) prompt and exit with a "kill the headless
+// instance?" prompt — dumping the debugee's full state and racing the attached
+// vscode-go client. This helper speaks rpc2 directly, so it only issues the
+// RPCs we want, prints nothing, and exits without disturbing the target or the
+// VS Code session.
+//
+// Usage: dlv-restart [addr]   (addr defaults to 127.0.0.1:2345)
+package main
+
+import (
+	"fmt"
+	"os"
+
+	"github.com/go-delve/delve/service/rpc2"
+)
+
+func main() {
+	addr := "127.0.0.1:2345"
+	if len(os.Args) > 1 {
+		addr = os.Args[1]
+	}
+
+	client := rpc2.NewClient(addr)
+
+	discarded, err := client.RestartFrom(false, "", false, nil, [3]string{}, false)
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "dlv-restart: Restart failed: %v\n", err)
+		os.Exit(1)
+	}
+	for _, d := range discarded {
+		fmt.Fprintf(os.Stderr, "discarded %s: %v\n", d.Breakpoint.Name, d.Reason)
+	}
+
+	// The restarted process begins halted, so resume it with Continue, then
+	// close the connection. --accept-multiclient keeps the server and target
+	// running while our short-lived client disconnects; an attached vscode-go
+	// client is undisturbed.
+	if err := client.Disconnect(true); err != nil {
+		fmt.Fprintf(os.Stderr, "dlv-restart: disconnect failed: %v\n", err)
+	}
+}