refactor(core): organize crates into six ownership layers

[limityan]

Summary

• Reorganize src/crates into six ownership layers: interfaces, assembly, adapters, services, execution, and contracts.
• Rename ambiguous physical crate folders for tool ownership: tool-contracts, tool-provider-groups, and tool-execution while keeping Cargo package/lib names stable for compatibility.
• Sync Cargo paths, boundary rules, self-tests, DeepReview path/risk classification, root/layer AGENTS docs, README, and core decomposition docs with the new layout.

Impact and Risk

• Intended as a structural/layout refactor; no product behavior or runtime logic change is introduced.
• Public Rust package names and crate import names are preserved to avoid downstream API churn.
• DeepReview path classification now resolves src/crates/<layer>/<crate> so layered paths do not collapse into one crate risk area.
• Old facade, integrations, product, surfaces, and ambiguous execution tool folder paths are removed from active workspace paths.

Verification

• git fetch gcwing main && git rebase gcwing/main
• git grep -n -E "src/crates/(facade|integrations|product|providers|surfaces)|crates/(facade|integrations|product|providers|surfaces)|src\\crates\\(facade|integrations|product|providers|surfaces)" HEAD -- Cargo.toml src/apps src/crates scripts src/web-ui docs AGENTS.md AGENTS-CN.md README.md README.zh-CN.md CONTRIBUTING.md CONTRIBUTING_CN.md
• git diff --check gcwing/main..HEAD
• cargo metadata --no-deps --format-version 1
• node --test scripts/check-core-boundaries.test.mjs
• node scripts/check-core-boundaries.mjs
• pnpm --dir src/web-ui run test:run src/shared/services/reviewTargetClassifier.test.ts src/shared/services/review-team/pathMetadata.test.ts src/shared/services/review-team/risk.test.ts src/shared/services/reviewTeamService.test.ts
• pnpm run check:repo-hygiene
• pnpm run i18n:contract:test
• cargo check -p bitfun-core --no-default-features
• cargo check -p bitfun-core --features product-full
• cargo check --workspace
• cargo test -p bitfun-agent-tools
• cargo test -p tool-runtime
• cargo test -p bitfun-tool-packs --features product-full
• cargo test -p bitfun-product-domains --no-default-features
• cargo test -p bitfun-product-capabilities