feat(config): add directory-aware label scoping for monorepos (fixes #541)

Adds automatic label filtering based on current working directory:
- New config option: directory.labels (maps directory patterns to labels)
- bd ready and bd list auto-apply label filtering when in matching directory
- Uses --label-any semantics (shows issues with any of the matching labels)

Config example:
```yaml
directory:
  labels:
    packages/maverick: maverick
    packages/agency: agency
```

When running `bd ready` from `packages/maverick/`, issues labeled
"maverick" are automatically shown first, without needing --label-any.

Closes #541

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

internal/config/config.go

@@ -116,6 +116,10 @@ func Initialize() error {
 	v.SetDefault("git.author", "")        // Override commit author (e.g., "beads-bot <beads@example.com>")
 	v.SetDefault("git.no-gpg-sign", false) // Disable GPG signing for beads commits
 
+	// Directory-aware label scoping (GH#541)
+	// Maps directory patterns to labels for automatic filtering in monorepos
+	v.SetDefault("directory.labels", map[string]string{})
+
 	// Read config file if it was found
 	if configFileSet {
 		if err := v.ReadInConfig(); err != nil {
@@ -196,6 +200,44 @@ func GetStringSlice(key string) []string {
 	return v.GetStringSlice(key)
 }
 
+// GetStringMapString retrieves a map[string]string configuration value
+func GetStringMapString(key string) map[string]string {
+	if v == nil {
+		return map[string]string{}
+	}
+	return v.GetStringMapString(key)
+}
+
+// GetDirectoryLabels returns labels for the current working directory based on config.
+// It checks directory.labels config for matching patterns.
+// Returns nil if no labels are configured for the current directory.
+func GetDirectoryLabels() []string {
+	cwd, err := os.Getwd()
+	if err != nil {
+		return nil
+	}
+
+	dirLabels := GetStringMapString("directory.labels")
+	if len(dirLabels) == 0 {
+		return nil
+	}
+
+	// Check each configured directory pattern
+	for pattern, label := range dirLabels {
+		// Support both exact match and suffix match
+		// e.g., "packages/maverick" matches "/path/to/repo/packages/maverick"
+		if strings.HasSuffix(cwd, pattern) || strings.HasSuffix(cwd, filepath.Clean(pattern)) {
+			return []string{label}
+		}
+		// Also try as a path prefix (user might be in a subdirectory)
+		if strings.Contains(cwd, "/"+pattern+"/") || strings.Contains(cwd, "/"+pattern) {
+			return []string{label}
+		}
+	}
+
+	return nil
+}
+
 // MultiRepoConfig contains configuration for multi-repo support
 type MultiRepoConfig struct {
 	Primary    string   // Primary repo path (where canonical issues live)