refactor(tools): share static provider group container

[limityan]

Summary

• Move the reusable static provider group container into bitfun-agent-tools.
• Keep core responsible for constructing concrete tools and preserving the existing provider group order.
• Update boundary checks and H1 planning docs so this slice cannot be mistaken for concrete tool/runtime migration.

Scope guard

This is the first H1 tool-runtime migration slice, but it is intentionally behavior-neutral. It does not move ToolUseContext, concrete tool implementations, runtime manifest assembly, collapsed unlock state, snapshot decoration, or GetToolSpec execution. Core still assembles the product tool providers and the existing registry/manifest snapshots remain the behavior guard.

Validation

• git merge-base --is-ancestor refs/remotes/gcwing/main HEAD
• git diff --check refs/remotes/gcwing/main..HEAD
• node scripts/check-core-boundaries.mjs
• cargo test -p bitfun-agent-tools --test tool_contracts
• cargo test -p bitfun-core registry_preserves --lib
• cargo test -p bitfun-core manifest_snapshot --lib
• cargo check -p bitfun-core --features product-full