feat: retain repo context and loop snapshots during compaction

[angeiv]

Summary

• expand the repo context pack with common package scripts and inject it into focused compaction input
• upgrade session memory to a backward-compatible v2 shape that keeps the latest loop result snapshot alongside compaction history and operator notes
• surface the latest loop snapshot through /memory and document the updated compaction/session-memory behavior

Verification

• pnpm build
• pnpm test