fix: stabilize quality score + suppress false tool call warnings + two-row statusline

Quality score jumping: enforce ResourceHealth monotonicity within a session.
Score can only decrease unless a compaction resets it.

False tool call warnings: superlinear scaling (x^1.3) gives warn=202/crit=324
for 1M context. Gate on fill_pct >= 50%.

Statusline: two-row layout, session duration always shown.

Bump to v5.6.13.