docs(quickapp): lead titles with the capability instead of the feature name

[tanghao-xiaomi]

Summary

Retitle the quick app AI Agent tutorial so the title leads with the capability, and keep the feature name as a code reference:

	Title
Before	openvela 快应用调用 velaclaw（端侧 AI Agent）教程
After	openvela 快应用调用端侧 AI Agent（@system.velaclaw）教程

Prose references to this tutorial are updated to match, so the docs name it consistently:

• quickapp/quickapp_guide_index.md — table link text, plus two prose mentions ("《velaclaw 教程》" -> "《端侧 AI Agent 教程》")
• ai_hardware/ai_agent_quickstart.md — cross-reference link text; the inline mention now uses the API in code form (@system.velaclaw)

Rationale

In a title the bare velaclaw reads as a product/brand name rather than as code, and the title is the most visible and most frequently quoted string in the doc set. Leading with the capability avoids that, while @system.velaclaw in parentheses keeps the API discoverable for anyone searching for it.

This also matches existing usage in ai_hardware/ai_hardware_track_guide.md, which already refers to this tutorial as "快应用调用 ai_agent" (that file needs no change).

What is NOT changed (intentional)

The code identifiers are the real API surface that quick apps call, so they are left untouched:

• @system.velaclaw, velaclaw.ask()
• velaclaw_client_open()
• the VELACLAW_DAEMON macro

Renaming any of these would break the examples. The filename quickapp_velaclaw.md is also kept as-is, since it matches the API name and renaming it would break existing internal and external links.

Scope

• 3 files, 13 insertions / 13 deletions
• Documentation wording only; no code, API or behavior changes.