Round-4 polish from Felix (#1): SEARCH_RESULT_LIMIT only has one consumer
today (PersonMentionEditor), so it risked masquerading as shared. Add a
one-line rationale that the symmetry with MAX_QUERY_LENGTH and
SEARCH_DEBOUNCE_MS — keeping all @mention knobs in one file — is the
intentional motivation, not a missed inlining.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
Single source of truth for MAX_QUERY_LENGTH, SEARCH_DEBOUNCE_MS, and
SEARCH_RESULT_LIMIT — MentionDropdown imports MAX_QUERY_LENGTH;
PersonMentionEditor imports the debounce + result-limit; the spec's
mirror now imports SEARCH_DEBOUNCE_MS so it can never drift. Unblocks
the displayName length-cap fix (Felix #3 on PR #629).
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>