refactor(tools): harden H1 migration baselines

[limityan]

Summary

• Rebase the H1 tool-runtime baseline slice onto latest gcwing/main and keep the PR as a single commit.
• Add focused migration baselines for builtin/readonly/collapsed tool manifests, explicit GetToolSpec insertion, and core-owned ToolExecutionContext to ToolUseContext runtime state propagation.
• Extract only the pure GetToolSpec load-observation to collapsed-tool-name collection helper into bitfun-agent-tools; core still owns ToolUseContext.unlocked_collapsed_tools, execution message parsing, runtime manifest assembly, GetToolSpecTool, snapshot decoration, and concrete tools.
• Update boundary checks and the core decomposition plan so this slice is recorded as H1 baseline work, not as runtime owner migration completion.

Functional Boundary

• No CLI/Desktop/Remote/ACP surface behavior changes.
• No concrete tool implementation moved out of core.
• No change to expanded/collapsed tool visibility rules, duplicate-load behavior, snapshot wrapping, cancellation handling, workspace services, or runtime handles.
• bitfun-agent-tools remains a lightweight contract/helper crate and must not own product tool runtime assembly or unlock state.

Verification

• rustfmt --edition 2024 --check src/crates/agent-tools/src/framework.rs src/crates/agent-tools/src/lib.rs src/crates/agent-tools/tests/tool_contracts.rs src/crates/core/src/agentic/execution/execution_engine.rs src/crates/core/src/agentic/tools/manifest_resolver.rs src/crates/core/src/agentic/tools/pipeline/tool_pipeline.rs src/crates/core/src/agentic/tools/registry.rs
• node scripts/check-core-boundaries.mjs
• git diff --check gcwing/main..HEAD
• cargo test -p bitfun-agent-tools --test tool_contracts
• cargo test -p bitfun-core registry_ --lib
• cargo test -p bitfun-core manifest_ --lib
• cargo test -p bitfun-core pipeline_preserves_core_owned_tool_context_without_portable_runtime_leak --lib
• cargo test -p bitfun-core collects_unlocked_collapsed_tools_from_visible_get_tool_spec_results --lib
• cargo check -p bitfun-core --features product-full