Clarify pending confirmation precedence

[rlippmann]

Summary

• Clarify that pending clarification handling takes precedence over compound-directive detection.
• Align the compound-directive clarification rules and standardized prompt documentation with that precedence.
• Clarify that quote characters have no special parsing semantics.

Why

The runtime already suspends directive parsing while a clarification is pending, but the compound-directive sections of the grammar spec did not explicitly state that precedence. This update removes the ambiguity without changing runtime behavior.

Scope checklist

• Diff is minimal and scoped to the requested behavior
• Python/spec parity is preserved (or mismatch is explicitly documented)
• Fixture semantics are respected (exact string vs non-empty null rule)
• No unrelated refactors
• Relevant validation was run (pytest for behavior changes, or docs-only/no-runtime-change)

Notes

Documentation-only clarification. No runtime behavior or package version change.