feat: session lifecycle wrapper with manifest capture and session logging

Refactor new/resume/open to use session.Run() which wraps child process launch with pre/post manifest capture and append-only session logging to logs/sessions.log. Bump version to 0.2.0.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

internal/session/run.go

@@ -0,0 +1,101 @@
+package session
+
+import (
+	"fmt"
+	"os"
+	"path/filepath"
+	"time"
+
+	"github.com/warrenronsiek/ctask/internal/shell"
+)
+
+// LaunchOpts configures a session launch.
+type LaunchOpts struct {
+	WsDir   string
+	EnvVars map[string]string
+	Agent   string
+	Mode    string
+	Slug    string
+	Shell   bool // true = interactive shell, false = agent
+}
+
+// manifestStartPath returns the path to the start manifest file.
+func manifestStartPath(wsDir string) string {
+	return filepath.Join(wsDir, ".ctask", "manifest-start.json")
+}
+
+// Run launches an agent or shell session with pre/post manifest capture and session logging.
+// Returns the child process error (for exit code propagation).
+func Run(opts LaunchOpts) error {
+	startTime := time.Now().UTC().Truncate(time.Second)
+
+	// Pre-session: capture start manifest
+	startManifest, err := CaptureManifest(opts.WsDir)
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "[ctask] warning: failed to capture start manifest: %v\n", err)
+		// Continue anyway — never block the user
+	}
+
+	if startManifest != nil {
+		mPath := manifestStartPath(opts.WsDir)
+		if err := WriteManifest(mPath, startManifest); err != nil {
+			fmt.Fprintf(os.Stderr, "[ctask] warning: failed to write start manifest: %v\n", err)
+		}
+	}
+
+	// Launch the session
+	var childErr error
+	if opts.Shell {
+		childErr = shell.ExecShell(opts.WsDir, opts.EnvVars, opts.Slug, opts.Mode)
+	} else {
+		// Print banner before agent launch
+		for _, line := range shell.BannerLines(opts.Mode, opts.Slug, opts.WsDir) {
+			fmt.Println(line)
+		}
+		childErr = shell.ExecAgent(opts.Agent, opts.WsDir, opts.EnvVars)
+	}
+
+	// Post-session: capture end manifest and log
+	endTime := time.Now().UTC().Truncate(time.Second)
+
+	if startManifest != nil {
+		if logErr := captureAndLog(opts, startManifest, startTime, endTime); logErr != nil {
+			fmt.Fprintf(os.Stderr, "[ctask] warning: session logging failed: %v\n", logErr)
+			// Keep manifest-start.json for debugging
+		} else {
+			// Clean up manifest-start.json on success
+			os.Remove(manifestStartPath(opts.WsDir))
+		}
+	}
+
+	return childErr
+}
+
+// captureAndLog captures the end manifest, diffs, and appends to session log.
+func captureAndLog(opts LaunchOpts, startManifest *Manifest, startTime, endTime time.Time) error {
+	endManifest, err := CaptureManifest(opts.WsDir)
+	if err != nil {
+		return fmt.Errorf("capturing end manifest: %w", err)
+	}
+
+	diff := DiffManifests(startManifest, endManifest)
+
+	info := &SessionInfo{
+		Agent:     opts.Agent,
+		Mode:      opts.Mode,
+		StartTime: startTime,
+		EndTime:   endTime,
+		Diff:      diff,
+	}
+
+	// For shell sessions, record "shell" as agent
+	if opts.Shell {
+		info.Agent = "shell"
+	}
+
+	if err := AppendSessionLog(opts.WsDir, info); err != nil {
+		return fmt.Errorf("appending session log: %w", err)
+	}
+
+	return nil
+}