Add markdown auto-format shortcut

[mvogttech]

Summary

• add a Ctrl+Shift+F command that formats the current document with a markdown formatter and status message
• keep the text buffer in sync with externally formatted content and document the new shortcut
• cover the formatter with unit tests to ensure headings, lists, and code fences stay stable

Testing

• npm test

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https://chatgpt.com/codex/tasks/task_e_68f0765b9bc483308febcb240d24fd80

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Preserve Markdown hard line break spaces

The formatter unconditionally trims all trailing whitespace from every non‑code line (const trimmedEnd = originalLine.replace(/\s+$/u, '')). In Markdown, two trailing spaces before a newline are the canonical way to force a hard line break. Invoking the new Ctrl+Shift+F shortcut on text that relies on this syntax will remove those spaces and the renderer will collapse the break back into the same paragraph, altering the document’s meaning. The formatter should skip trimming when a line intentionally ends with two spaces.

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