chore: prune solo-venus-cc.md ship-log accretion (session-ledger → git/bwi)

solo-venus-cc.md is 205 lines; ~half is per-WI ship-log ('VENUS-136 SWEEP COMPLETE', 'W2 SHIPPED <sha>', etc.) which the file's own header bans ('durable rules, not a session ledger') and which loads every solo session (it's the ONLY file solo loads). Prune: keep durable rules (auth/DB/push/PTD/safety/domain), move shipped-WI changelogs to git log + bwi. Owner: solo-venus-cc self-prunes (its own knowledge file). Cost lever flagged in Elazar retro of fd228ad.