feat: add scope_id tagging to pact-memory entries

[michael-wojcik]

Context

Deferred from PACT v3 Phase D (original D1-D3 scope). Tracked for v3.1+.

Description

Tag pact-memory entries with a scope_id field to enable scope-filtered retrieval during scoped orchestration. When sub-scopes execute via rePACT (e.g., backend, frontend, database), lessons and decisions from each sub-scope would be tagged with their scope identifier.

This enables:

• Scope-filtered memory search ("show me lessons from the backend sub-scope")
• Cross-scope pattern detection ("what patterns recur across sub-scopes?")
• Scope-aware context loading for rePACT cycles

Current State

• No real-world scoped orchestration usage yet — scope detection and ATOMIZE/CONSOLIDATE phases are documented but untested in production
• Agent persistent memory (memory: user, added in v2.8.0) provides partial domain-level separation implicitly (each specialist accumulates its own domain expertise)
• scope_id is defined in scope contracts (pact-scope-contract.md) but not yet consumed by pact-memory

Priority

Low — blocked on real-world scoped orchestration usage to validate the need.

References

• PR feat: Phase D revised — memory rationalization, agent persistent memory, expanded verification (v2.8.0) #156 (Phase D revised, v2.8.0)
• pact-plugin/protocols/pact-scope-contract.md (scope_id definition)
• pact-plugin/skills/pact-memory/ (memory system)