docs: live site in plain language, for readers who do not code

[cskwork]

What

The GitHub Pages site (docs/index.html) is rewritten so that a reader who does not write code can follow it. That is the page's purpose; the v0.22.0 update made it current but left it written for developers.

• No file names, commands, flags, or kit jargon in the story sections. A gate is a "checkpoint" (확인 지점); stages are named for what they do (Understand, Describe, Plan, Build, Deliver, Follow up); lazymode is "which checkpoints wait for a person".
• The hero keeps its terminal frame but shows a plain exchange: the AI is ready, the checkpoint says a person has not approved yet, the person approves, the work goes on.
• "What you get" has five entries (was eight). "What it cannot do" keeps the honest limit.
• Commands and file names appear only in the last section, "For the person who sets it up" (설치하는 분께).
• A comment at the top of the file records the audience rule.
• English and Korean say the same things. 46.3 → 41.8 KB.

No kit file changed; no version bump.

Verified

• HTML parses, tags balance, anchors and local links resolve; the page script passes node --check.
• 68 text keys in the page, 68 in the Korean table, none missing or unused.
• A scan of the visible text before the install section finds none of the listed technical terms in either language.
• Rendered in headless Chrome in both languages; both sets of copy read in full.

Not verified

• No reader outside the project has read it.