[Alox1d]

Problem

The article editor rejects its input rules and slash insert menu inside toggle (Details) content. The two input handlers only accept isActiveTopLevelParagraph(), which excludes paragraphs nested inside Details.

Reported in #31518 and #31516.

Changes

• Introduce State::activeParagraphAllowsInsertShortcuts().
• Permit the existing input rules and insert suggestions only for top-level paragraphs and paragraph blocks directly inside a Details container.
• Keep the previous restrictions on quote content, list items, table cells, headings and the toggle title.

The existing MatchInputRule() and block insertion logic are reused, without adding new UI or changing shortcut syntax.

Validation

• Compiled the actual two production State predicate implementations, extracted against a minimal C++20 model of the existing block paths; regression checks pass for top-level paragraphs, nested Details paragraphs and the excluded quote/list/table/heading/title cases.
• git diff --check: pass.
• Not yet verified in the full Telegram Desktop build or GUI. This isolated checkout has no configured CMake/Qt build tree. Opening as a draft until that validation is available.

This PR addresses both reports because the two handlers have the same eligibility guard.

[CLAassistant]

All committers have signed the CLA.