feat(core): add generic session inbox - #42109

Summary

• replace the input-specific pending model with a generic per-session inbox for user, synthetic, compaction, and move items
• add durable inbox lifecycle events, generic steer/queue scheduling, and atomic delivery batches for compaction and move
• add the pending-only session_inbox table and expose inbox list, cancel, steer, and queue APIs across generated clients and UI consumers
• allow every item type to stack independently with either delivery mode

Verification

• repository pre-push typecheck: 32 packages passed
• core Bus, inbox, projector, prompt, move, compaction, and runner suites: 255 tests passed
• TUI selected suites: 102 tests passed
• client suites: 29 tests passed
• SDK Next suites: 12 tests passed
• CLI selected suites: 33 tests passed
• App reducer suite: 6 tests passed
• Schema contract and event manifest suites passed
• protocol/client/www generated checks passed
• migration consistency check passed