fix(core): ignore project shell hooks

[BunsDev]

Motivation

• Project-provided shell hooks were merged into the effective settings and could be executed for provider-returned tool calls, enabling arbitrary shell execution from an attacker-controlled repository; hooks coming from untrusted project settings must not be auto-registered.
• The goal is to keep repository-scoped, non-executable preferences while preventing repositories from injecting hooks that run in response to model/provider events.

Description

• Clear config.hooks in Settings::sanitize_project_settings so project-provided hooks are dropped before merging into global settings.
• Extend the existing project_settings_do_not_merge_mcp_servers unit test to include a trusted global PreToolUse hook and a project-local PreToolUse hook, then assert that only the global hook remains after merge.
• Change is limited to src-rust/crates/core/src/lib.rs (settings sanitization and test fixture); no behavioral changes to hook execution logic.

Testing

• Ran cargo test -p claurst-core config::tests::project_settings_do_not_merge_mcp_servers -- --exact, and the test passed.
• Ran cargo check -p claurst-core, which succeeded.
• cargo check --workspace was attempted but blocked by a missing system dependency (alsa.pc) required by alsa-sys in this environment.
• Repository-wide cargo fmt --all --check and cargo clippy -p claurst-core --all-targets -- -D warnings were not completed due to unrelated repo-wide formatting and clippy findings outside the scope of this patch.

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Codex Task

[Copilot]

Pull request overview

This PR hardens settings merging in claurst-core by preventing repository-scoped (project-local) settings from registering shell hooks that could execute commands in response to model/provider events, while preserving trusted global settings behavior.

Changes:

• Drop project-provided hook registrations by clearing config.hooks during Settings::sanitize_project_settings.
• Extend the existing settings-merge unit test to include both global and project PreToolUse hooks and assert only the global hook survives the merge.

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