feat(v0.3): add seed dir and project root resolvers in config

ResolveSeedDir, ResolveProjectSeedDir, and ResolveProjectRoot read
the v0.3 environment variables (CTASK_SEED_DIR,
CTASK_SEED_PROJECT_DIR, CTASK_PROJECT_ROOT) and fall back to
platform defaults under %APPDATA%\ctask or ~/.config/ctask. The
expandPath helper handles tilde expansion + abs-path resolution
once for all resolvers.

internal/config/config.go

@@ -3,6 +3,7 @@ package config
 import (
 	"os"
 	"path/filepath"
+	"runtime"
 	"strings"
 )
 
@@ -14,16 +15,7 @@ func ResolveRoot() string {
 		home, _ := os.UserHomeDir()
 		return filepath.Join(home, "ai-workspaces")
 	}
-	// Expand leading tilde
-	if strings.HasPrefix(root, "~/") || root == "~" {
-		home, _ := os.UserHomeDir()
-		root = filepath.Join(home, root[2:])
-	}
-	abs, err := filepath.Abs(root)
-	if err != nil {
-		return root
-	}
-	return abs
+	return expandPath(root)
 }
 
 // ResolveAgent returns the agent command.
@@ -36,6 +28,37 @@ func ResolveAgent() string {
 	return agent
 }
 
+// ResolveSeedDir returns the user general seed directory.
+// Reads CTASK_SEED_DIR; falls back to %APPDATA%\ctask\seed on Windows or
+// ~/.config/ctask/seed on Unix.
+func ResolveSeedDir() string {
+	if v := os.Getenv("CTASK_SEED_DIR"); v != "" {
+		return expandPath(v)
+	}
+	return defaultSeedDir("seed")
+}
+
+// ResolveProjectSeedDir returns the user project seed directory.
+// Reads CTASK_SEED_PROJECT_DIR; falls back to %APPDATA%\ctask\seed-project on Windows
+// or ~/.config/ctask/seed-project on Unix.
+func ResolveProjectSeedDir() string {
+	if v := os.Getenv("CTASK_SEED_PROJECT_DIR"); v != "" {
+		return expandPath(v)
+	}
+	return defaultSeedDir("seed-project")
+}
+
+// ResolveProjectRoot returns the project workspace root override.
+// Returns empty string if CTASK_PROJECT_ROOT is not set; callers should fall back
+// to ResolveRoot() in that case.
+func ResolveProjectRoot() string {
+	v := os.Getenv("CTASK_PROJECT_ROOT")
+	if v == "" {
+		return ""
+	}
+	return expandPath(v)
+}
+
 // EnvVars returns the environment variables to export into child sessions.
 func EnvVars(slug, mode, root, workspace, category string) map[string]string {
 	return map[string]string{
@@ -46,3 +69,30 @@ func EnvVars(slug, mode, root, workspace, category string) map[string]string {
 		"CTASK_CATEGORY":  category,
 	}
 }
+
+// defaultSeedDir returns the platform-default location for a seed directory leaf.
+func defaultSeedDir(leaf string) string {
+	if runtime.GOOS == "windows" {
+		appData := os.Getenv("APPDATA")
+		if appData == "" {
+			home, _ := os.UserHomeDir()
+			return filepath.Join(home, "AppData", "Roaming", "ctask", leaf)
+		}
+		return filepath.Join(appData, "ctask", leaf)
+	}
+	home, _ := os.UserHomeDir()
+	return filepath.Join(home, ".config", "ctask", leaf)
+}
+
+// expandPath expands a leading ~/ and resolves to an absolute path when possible.
+func expandPath(p string) string {
+	if strings.HasPrefix(p, "~/") || p == "~" {
+		home, _ := os.UserHomeDir()
+		p = filepath.Join(home, p[1:])
+	}
+	abs, err := filepath.Abs(p)
+	if err != nil {
+		return p
+	}
+	return abs
+}