Skill icon branding, empty directory indexing in @-completion, and headless exit code fixes

Adds skill icon branding with Unicode alignment in catalogs and slash commands, indexes empty directories in @ path completion, auto-approves workspace-scoped read access in review mode, and fixes headless print mode error handling.

• Added skill icon and visual branding support across the CLI, displaying emoji icons declared under metadata.icon in SKILL.md frontmatter across the /skills catalog list view, detail inspection headers, and slash command autocompletion popups with multi-byte Unicode display width calculation.
• Improved @ file path autocompletion by indexing empty directories alongside files in ripgrep search results, enabling directory-only and unpopulated structures to be traversed.
• Improved permission management by automatically granting workspace-scoped read access under the default review mode, removing repetitive approval prompts for reading or listing workspace files while strictly maintaining confirmation for modifications and external access.
• Improved Git repository inspection performance by skipping recursive submodule worktree scans while continuing to track commit pointer updates.
• Fixed print mode (-p/--print, including --output-format json and stream-json) treating benign tool execution errors and permission denials as fatal run failures with non-zero exit codes.
• Fixed the CLI overwriting and discarding unparsed configuration in settings.json when encountering an unrecognized setting value or syntax error on startup.
• Fixed /skills, /plugins, /agents, and /hooks commands reporting that no customizations were found when invoked without an explicit agent configuration by mounting built-in customizations.
• Fixed CJK draft jitter in the main prompt by normalizing boundary whitespace in streaming transcript updates.
• Fixed the conversation spinner animation loop continuing to tick in the background after turn completion, eliminating idle CPU wakeups.