fix(core): relax active skill tool restrictions by default

[Aspdelus]

Summary

• Stop active skill allowed-tools from globally denying ordinary session tool calls by default.
• Add enforceActiveSkillToolRestrictions / with_active_skill_tool_restrictions(true) as a compatibility switch for legacy behavior.
• Keep skill-local allowed-tools enforced inside Skill child execution contexts.
• Treat allowed-tools: "*" as a skill grant wildcard without bypassing permission policy, hooks, HITL, or AHP.

Tests

• cargo fmt --all -- --check
• rustfmt --edition 2021 --check sdk/node/src/lib.rs sdk/python/src/lib.rs
• git diff --check
• cargo test -p a3s-code-core
• cargo test --manifest-path sdk/node/Cargo.toml
• cargo test --manifest-path sdk/python/Cargo.toml