feat(skills): add --allow-hidden-dirs flag to preview command

Add support for the --allow-hidden-dirs flag in `gh skill preview`,
matching the existing pattern in `gh skill install`. This allows users
to preview skills located in hidden directories (e.g. .claude/skills/,
.agents/skills/).

Changes:
- Add AllowHiddenDirs field to PreviewOptions
- Register --allow-hidden-dirs flag on the preview command
- Switch from DiscoverSkills to DiscoverSkillsWithOptions to get all
  skills including hidden-dir ones
- Add filterHiddenDirSkills to exclude hidden-dir skills by default,
  showing a hint when they are found but excluded
- Print a warning when --allow-hidden-dirs is used and hidden skills
  are present
- Return an error when only hidden-dir skills exist without the flag

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: Copilot

internal/skills/discovery/discovery.go

@@ -101,6 +101,26 @@ func HasHiddenDirSkills(skills []Skill) bool {
 	return false
 }
 
+// HiddenDirFilterResult holds the outcome of partitioning skills into standard
+// and hidden-dir buckets.
+type HiddenDirFilterResult struct {
+	Standard    []Skill
+	HiddenCount int
+}
+
+// PartitionHiddenDirSkills splits skills into standard and hidden-dir groups.
+func PartitionHiddenDirSkills(skills []Skill) HiddenDirFilterResult {
+	var r HiddenDirFilterResult
+	for _, s := range skills {
+		if s.IsHiddenDirConvention() {
+			r.HiddenCount++
+		} else {
+			r.Standard = append(r.Standard, s)
+		}
+	}
+	return r
+}
+
 // ResolvedRef contains the resolved git reference and its SHA.
 type ResolvedRef struct {
 	Ref string // fully qualified ref (refs/heads/*, refs/tags/*) or commit SHA

pkg/cmd/skills/install/install.go

@@ -1180,10 +1180,9 @@ func kiroResourcePath(installDir, gitRoot string) string {
 	return filepath.ToSlash(installDir)
 }
 
-// filterHiddenDirSkills separates hidden-dir skills from the full list and
-// applies the --allow-hidden-dirs flag logic. When the flag is set, all skills
-// are returned and a warning is printed. When the flag is not set, hidden-dir
-// skills are excluded and an error is returned if no standard skills remain.
+// filterHiddenDirSkills applies the --allow-hidden-dirs flag logic. When the
+// flag is set, all skills are returned with a warning. Otherwise, hidden-dir
+// skills are excluded with an error if no standard skills remain.
 func filterHiddenDirSkills(opts *InstallOptions, allSkills []discovery.Skill) ([]discovery.Skill, error) {
 	cs := opts.IO.ColorScheme()
 
@@ -1198,25 +1197,16 @@ func filterHiddenDirSkills(opts *InstallOptions, allSkills []discovery.Skill) ([
 		return allSkills, nil
 	}
 
-	var standard []discovery.Skill
-	var hiddenCount int
-	for _, s := range allSkills {
-		if s.IsHiddenDirConvention() {
-			hiddenCount++
-		} else {
-			standard = append(standard, s)
-		}
-	}
-
-	if len(standard) == 0 && hiddenCount > 0 {
+	r := discovery.PartitionHiddenDirSkills(allSkills)
+	if len(r.Standard) == 0 && r.HiddenCount > 0 {
 		return nil, fmt.Errorf(
 			"no standard skills found, but %d skill(s) exist in hidden directories\n"+
 				"  Use --allow-hidden-dirs to include them",
-			hiddenCount,
+			r.HiddenCount,
 		)
 	}
 
-	return standard, nil
+	return r.Standard, nil
 }
 
 // checkUpstreamProvenance fetches the skill's SKILL.md via the contents API

pkg/cmd/skills/preview/preview.go

@@ -32,9 +32,10 @@ type PreviewOptions struct {
 	ExecutablePath string
 	RenderFile     func(string, string) string
 
-	RepoArg   string
-	SkillName string
-	Version   string // resolved from @suffix on SkillName
+	RepoArg         string
+	SkillName       string
+	Version         string // resolved from @suffix on SkillName
+	AllowHiddenDirs bool   // include skills in dot-prefixed directories
 
 	repo ghrepo.Interface
 }
@@ -110,6 +111,8 @@ func NewCmdPreview(f *cmdutil.Factory, telemetry ghtelemetry.CommandRecorder, ru
 		},
 	}
 
+	cmd.Flags().BoolVar(&opts.AllowHiddenDirs, "allow-hidden-dirs", false, "Include skills in hidden directories (e.g. .claude/skills/, .agents/skills/)")
+
 	return cmd
 }
 
@@ -151,12 +154,17 @@ func previewRun(opts *PreviewOptions) error {
 	}
 
 	opts.IO.StartProgressIndicatorWithLabel("Discovering skills")
-	skills, err := discovery.DiscoverSkills(apiClient, hostname, owner, repoName, resolved.SHA)
+	allSkills, err := discovery.DiscoverSkillsWithOptions(apiClient, hostname, owner, repoName, resolved.SHA, discovery.DiscoverOptions{})
 	opts.IO.StopProgressIndicator()
 	if err != nil {
 		return err
 	}
 
+	skills, err := filterHiddenDirSkills(opts, allSkills)
+	if err != nil {
+		return err
+	}
+
 	sort.Slice(skills, func(i, j int) bool {
 		return skills[i].DisplayName() < skills[j].DisplayName()
 	})
@@ -388,6 +396,39 @@ func isMarkdownFile(filePath string) bool {
 	}
 }
 
+// filterHiddenDirSkills applies the --allow-hidden-dirs flag logic. When the
+// flag is set, all skills are returned with a warning. Otherwise, hidden-dir
+// skills are excluded with a hint or error.
+func filterHiddenDirSkills(opts *PreviewOptions, allSkills []discovery.Skill) ([]discovery.Skill, error) {
+	cs := opts.IO.ColorScheme()
+
+	if opts.AllowHiddenDirs {
+		if discovery.HasHiddenDirSkills(allSkills) {
+			fmt.Fprint(opts.IO.ErrOut, heredoc.Docf(`
+				%[1]s Skills in hidden directories (e.g. .claude/, .agents/) may be installed
+				  copies from another publisher. Verify the skill's origin and check for a
+				  canonical source.
+			`, cs.WarningIcon()))
+		}
+		return allSkills, nil
+	}
+
+	r := discovery.PartitionHiddenDirSkills(allSkills)
+	if r.HiddenCount > 0 {
+		if len(r.Standard) == 0 {
+			return nil, fmt.Errorf(
+				"no standard skills found, but %d skill(s) exist in hidden directories\n"+
+					"  Use --allow-hidden-dirs to include them",
+				r.HiddenCount,
+			)
+		}
+		fmt.Fprintf(opts.IO.ErrOut, "%s %d skill(s) in hidden directories were excluded, use --%s to include them\n",
+			cs.Yellow("!"), r.HiddenCount, "allow-hidden-dirs")
+	}
+
+	return r.Standard, nil
+}
+
 func selectSkill(opts *PreviewOptions, skills []discovery.Skill) (discovery.Skill, error) {
 	if opts.SkillName != "" {
 		for _, s := range skills {