Refactor core owner crate boundaries

[limityan]

Summary

• Harden the runtime boundary contracts used before the next service/tool owner migrations.
• Add the P2 medium-grain owner crates: bitfun-services-core, bitfun-services-integrations, bitfun-agent-tools, bitfun-tool-packs, and bitfun-product-domains.
• Preserve legacy bitfun-core import paths through facade re-exports while keeping the migrated slices behavior-preserving.
• Update the core decomposition plan with the latest origin/main Deep Review boundary constraints for P2/P3 follow-up work.

Safety Notes

• Product default features, product-full assembly, build scripts, installer scripts, and release scripts are not changed.
• Latest Deep Review runtime additions from main remain core-owned for now: context profile, evidence ledger, capacity/cost/queue controls, and session manifest/cache persistence.
• Follow-up P2/P3 work still needs explicit port/provider contracts before moving heavy service, concrete tool, miniapp runtime, or function-agent runtime logic.

Verification

• git diff --check origin/main..HEAD
• cargo check --workspace

Current branch is rebased on origin/main at f77eefe4.