Function isBannedLocalizedBriefH1

Return true when h1 is template / placeholder boilerplate that must not be used as the SERP <title>.

Three rejection layers:

1. Any banned-phrase match from LOCALIZED_BRIEF_H1_BANNED_PATTERNS.
2. The bare boilerplate Executive Brief (case- and emoji-tolerant) — identical to the gate's h1Plain === 'executive brief' check.
3. The empty string after emoji + connector stripping.

Pure function — exported for tests.