Split internal/daemon vm.go and guest_sessions.go by concern

vm.go (1529 LOC) splits into vm_create, vm_lifecycle, vm_set, vm_stats,
vm_disk, vm_authsync; firecracker/DNS/helpers stay in vm.go.

guest_sessions.go (1266 LOC) splits into session_controller,
session_lifecycle, session_attach, session_stream; scripts and helpers
stay in guest_sessions.go.

Mechanical move only. No behavior change. Adds doc.go and
ARCHITECTURE.md capturing subsystem map and current lock ordering as
the baseline for the upcoming subsystem extraction.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

internal/daemon/session_stream.go

@@ -0,0 +1,119 @@
+package daemon
+
+import (
+	"bytes"
+	"context"
+	"errors"
+	"fmt"
+	"net"
+	"path/filepath"
+	"strings"
+
+	"banger/internal/api"
+	"banger/internal/guest"
+	"banger/internal/model"
+	"banger/internal/system"
+)
+
+func (d *Daemon) GuestSessionLogs(ctx context.Context, params api.GuestSessionLogsParams) (api.GuestSessionLogsResult, error) {
+	vm, err := d.FindVM(ctx, params.VMIDOrName)
+	if err != nil {
+		return api.GuestSessionLogsResult{}, err
+	}
+	session, err := d.findGuestSession(ctx, vm.ID, params.SessionIDOrName)
+	if err != nil {
+		return api.GuestSessionLogsResult{}, err
+	}
+	streamName := strings.TrimSpace(params.Stream)
+	if streamName == "" {
+		streamName = "stdout"
+	}
+	tailLines := params.TailLines
+	if tailLines <= 0 {
+		tailLines = guestSessionLogTailLine
+	}
+	path := session.StdoutLogPath
+	if streamName == "stderr" {
+		path = session.StderrLogPath
+	}
+	content, err := d.readGuestSessionLog(ctx, vm, session, streamName, tailLines)
+	if err != nil {
+		return api.GuestSessionLogsResult{}, err
+	}
+	return api.GuestSessionLogsResult{Session: session, Stream: streamName, Path: path, Content: content}, nil
+}
+
+func (d *Daemon) SendToGuestSession(ctx context.Context, params api.GuestSessionSendParams) (api.GuestSessionSendResult, error) {
+	vm, err := d.FindVM(ctx, params.VMIDOrName)
+	if err != nil {
+		return api.GuestSessionSendResult{}, err
+	}
+	session, err := d.findGuestSession(ctx, vm.ID, params.SessionIDOrName)
+	if err != nil {
+		return api.GuestSessionSendResult{}, err
+	}
+	if session.StdinMode != model.GuestSessionStdinPipe {
+		return api.GuestSessionSendResult{}, errors.New("session does not have a stdin pipe")
+	}
+	if session.Status != model.GuestSessionStatusRunning {
+		return api.GuestSessionSendResult{}, fmt.Errorf("session is not running (status=%s)", session.Status)
+	}
+	if vm.State != model.VMStateRunning || !system.ProcessRunning(vm.Runtime.PID, vm.Runtime.APISockPath) {
+		return api.GuestSessionSendResult{}, fmt.Errorf("vm %q is not running", vm.Name)
+	}
+	if len(params.Payload) == 0 {
+		return api.GuestSessionSendResult{Session: session}, nil
+	}
+	client, err := d.dialGuest(ctx, net.JoinHostPort(vm.Runtime.GuestIP, "22"))
+	if err != nil {
+		return api.GuestSessionSendResult{}, fmt.Errorf("dial guest: %w", err)
+	}
+	defer client.Close()
+	tmpPath := fmt.Sprintf("/tmp/banger-send-%s.bin", session.ID[:8])
+	var uploadLog bytes.Buffer
+	if err := client.UploadFile(ctx, tmpPath, 0o600, params.Payload, &uploadLog); err != nil {
+		return api.GuestSessionSendResult{}, fmt.Errorf("upload payload: %w", err)
+	}
+	sendScript := fmt.Sprintf(
+		"set -euo pipefail\ncat %s >> %s\nrm -f %s\n",
+		guestShellQuote(tmpPath),
+		guestShellQuote(guestSessionStdinPipePath(session.ID)),
+		guestShellQuote(tmpPath),
+	)
+	var sendLog bytes.Buffer
+	if err := client.RunScript(ctx, sendScript, &sendLog); err != nil {
+		return api.GuestSessionSendResult{}, fmt.Errorf("send to session: %w: %s", err, strings.TrimSpace(sendLog.String()))
+	}
+	return api.GuestSessionSendResult{Session: session, BytesWritten: len(params.Payload)}, nil
+}
+
+func (d *Daemon) readGuestSessionLog(ctx context.Context, vm model.VMRecord, session model.GuestSession, stream string, tailLines int) (string, error) {
+	if vm.State == model.VMStateRunning && system.ProcessRunning(vm.Runtime.PID, vm.Runtime.APISockPath) {
+		client, err := guest.Dial(ctx, net.JoinHostPort(vm.Runtime.GuestIP, "22"), d.config.SSHKeyPath)
+		if err != nil {
+			return "", err
+		}
+		defer client.Close()
+		path := session.StdoutLogPath
+		if stream == "stderr" {
+			path = session.StderrLogPath
+		}
+		var output bytes.Buffer
+		script := fmt.Sprintf("set -euo pipefail\nif [ -f %s ]; then tail -n %d %s; fi\n", guestShellQuote(path), tailLines, guestShellQuote(path))
+		if err := client.RunScript(ctx, script, &output); err != nil {
+			return "", formatGuestSessionStepError("read guest session log", err, output.String())
+		}
+		return output.String(), nil
+	}
+	runner := d.runner
+	if runner == nil {
+		runner = system.NewRunner()
+	}
+	workMount, cleanup, err := system.MountTempDir(ctx, runner, vm.Runtime.WorkDiskPath, false)
+	if err != nil {
+		return "", err
+	}
+	defer cleanup()
+	logPath := filepath.Join(workMount, guestSessionRelativeStateDir(session.ID), stream+".log")
+	return tailFileContent(logPath, tailLines)
+}