refactor(tools): complete H1 provider boundary

[limityan]

Summary

• Complete the H1 tool provider boundary by moving product provider group planning into bitfun-tool-packs while keeping concrete tool materialization in bitfun-core.
• Route GetToolSpec result adaptation through the provider-backed runtime facade and keep ToolUseContext, unlock state, concrete tools, and product registry snapshots core-owned.
• Update boundary guardrails and docs so H1 is closed without implying concrete tool/runtime owner migration.
• Fix SubagentSessionLinked routing in CLI and remote-connect trackers after the latest event-shape changes.

Adversarial Review Notes

• Scope check: the diff is one commit against latest gcwing/main; it does not move concrete tools, ToolUseContext, workspace services, snapshot wrappers, or product runtime handles out of core.
• Behavior check: provider ids and tool order are locked by new tool-packs and core registry tests; GetToolSpec and remote-connect regressions are covered by focused tests.
• Documentation check: AGENTS.md, module AGENTS files, and decomposition docs now state that tool-packs owns provider planning only, not concrete runtime behavior.

Validation

• node scripts/check-core-boundaries.mjs
• git diff --check gcwing/main..HEAD
• cargo check --workspace
• cargo test -p bitfun-services-integrations --features remote-connect --test remote_connect_contracts
• cargo test -p bitfun-agent-tools --test tool_contracts
• cargo test -p bitfun-tool-packs --lib
• cargo test -p bitfun-core builtin_static_tool_providers_follow_tool_pack_group_plan --lib
• cargo test -p bitfun-core get_tool_spec --lib
• cargo test --workspace