Search relevance weighting v2

Search quality is acceptable for exact RFD numbers but weak for concept-level queries where terms appear in long comment threads. The proposed v2 weighting favors title and summary text, then proposal body, and finally comment bodies with a lower multiplier. We should evaluate this against a fixed benchmark set of 40 representative queries gathered from team usage and compare top-5 precision with the current tuning. Open questions include how aggressively to de-prioritize stale threads and whether archived discussions should receive a recency penalty rather than being filtered entirely.