[FEATURE] Auto-initialism aliases for custom skills (e.g., `/itp` → `/image-to-prompt`)

Preflight Checklist

• [x] I have searched existing requests and this feature hasn't been requested yet
• [x] This is a single feature request (not multiple features)

Problem Statement

EN: Custom skills often have descriptive but lengthy names (e.g., /image-to-prompt, /save-ob-chaos-excalidraw). Typing these repeatedly is tedious and error-prone. Unlike built-in commands, skills live in nested directories and their slash command names are derived from folder names, giving users no way to create shorter invocations without renaming the entire skill folder.

ZH: 自定义 skill 的名称通常描述性强但冗长（如 /image-to-prompt、/save-ob-chaos-excalidraw）。反复输入既繁琐又容易出错。与内置命令不同，skill 的斜杠命令名称直接取自文件夹名，用户无法在不重命名整个 skill 文件夹的情况下创建更短的调用方式。

Proposed Solution

EN: Add an aliases field to settings.json (or a dedicated ~/.claude/aliases.json) that maps short names to existing skill commands:

{
  "skillAliases": {
    "itp": "image-to-prompt",
    "stec": "save-to-excalidraw-collections"
  }
}

Typing /itp in the prompt would resolve to /image-to-prompt and invoke the skill as usual. This should work for both global (~/.claude/skills/) and project-level (.claude/skills/) skills. or, more progressive, be default options.

ZH: 在 settings.json 中新增 skillAliases 字段（或独立的 ~/.claude/aliases.json），将短名称映射到已有的 skill 命令。输入 /itp 时自动解析为 /image-to-prompt 并正常调用。全局和项目级 skill 均应支持。或者，无需设置 alias，直接把单词首字拼接，作为默认选项。

Alternative Solutions

EN:

1. Rename skill folders — breaks descriptive naming and may conflict with shared configs across teams.
2. Shell-level aliases (e.g., alias itp='claude -p "/image-to-prompt"') — only works in headless/CLI mode, not in interactive TUI.
3. Symlink skill folders — creates maintenance burden.

ZH:

1. 重命名 skill 文件夹 — 破坏描述性命名，且可能与团队共享配置冲突。
2. Shell 别名（如 alias itp='claude -p "/image-to-prompt"'）— 仅适用于 headless/CLI 模式，不适用于交互式 TUI。
3. 符号链接 skill 文件夹 — 增加维护负担。

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EN: Medium — won't fix a critical bug, but would meaningfully reduce repetitive strain for power users who maintain a large skill library. Call it an occupational hazard mitigation. 🦴

ZH: Medium — 不会修复关键 bug，但能显著减轻维护大量 skill 的重度用户的重复输入负担。可以缓解我的职业病。🦴

Priority

Medium - Would be very helpful

Feature Category

Interactive mode (TUI)

Use Case Example

EN:
| Alias | Resolves To | Saves |
|-------|-------------|-------|
| /itp | /image-to-prompt | 15 chars |
| /stef | /save-to-excalidraw-fav | 24 chars |

same result, less friction.

ZH: 效果相同，摩擦更小。

Related: #32785, #14576

Additional Context

_No response_