fix(doc): strip duplicate title H1 on the JSONML doc-create path

[PeterGuy326]

Problem

dws doc create renders --name as the page title. When the body also opens with an H1 of the same text, the document shows the title twice — the "两个标题头" effect.

PR #448 fixed this only on the markdown path (stripLeadingDuplicateTitleHeading). The JSONML path (--content-format jsonml) was never covered: rich docs — tables, callouts, styled blocks — go through create_document + update_document(jsonml=...), which writes the body verbatim. So a leading h1 whose text equals the document name survives and renders twice.

This was hit in practice by a richly-formatted doc (tables + styled 🧪 callout) created via the JSONML path — the leading H1 duplicating the page title was not stripped.

Fix

Add stripLeadingDuplicateTitleJSONML, the JSONML counterpart of the markdown guard, wired into the format == "jsonml" branch of doc create right after prepareDocJSONMLBody and before update_document:

• Parse the marshaled JSONML body.
• Skip an optional ["root", {}, ...] wrapper.
• Drop the first node only when it's an h1 whose concatenated leaf text equals --name (trimmed, case-insensitive).
• Any parse failure or non-match leaves the body untouched — a valid write is never blocked.
• Emits the same stderr note as the markdown path.

Scope matches #448 exactly: only a leading h1 that exactly equals the name is removed; h2+, distinct headings, and names that merely share a prefix are kept.

Tests

• TestStripLeadingDuplicateTitleJSONML — unit table: root-wrapped, nested leaf text, bare body (no wrapper), case-insensitive, distinct heading kept, non-h1 kept, invalid JSON untouched.
• TestDocCreateStripsDuplicateTitleJSONML — end-to-end through the real doc create --content-format jsonml command, asserting the forwarded update_document jsonml has the duplicate h1 removed and the body content preserved.

ok  github.com/DingTalk-Real-AI/dingtalk-workspace-cli/internal/helpers