fix(tools): prevent composite disabled_toolsets from stripping explicitly enabled tools

[isheng-eqi]

What does this PR do?

Composite toolsets like safe and debugging re-list tools shared by other enabled toolsets. When a composite appears in disabled_toolsets, subtracting the full toolset silently strips tools from explicitly enabled toolsets — the model receives Tools: 0 with no warning, and tool calls fail silently.

The existing non-core-delta protection from #33924 covers hermes-* bundles and posture toolsets (coding) but missed safe and debugging — any composite with includes.

Related Issue

Fixes #58281

Type of Change

• Bug fix

Changes Made

• model_tools.py: Extend _compute_tool_definitions() to detect any composite toolset with includes — not just hermes-* and postures. Use bundle_non_core_tools() for these composites so shared tools from enabled toolsets are preserved.
• tests/test_disabled_toolset_enabled_preservation.py: 6 tests covering debugging, safe, coding, hermes-cli, and edge cases

How to Test

1. Set agent.enabled_toolsets: [terminal, file] and agent.disabled_toolsets: [debugging]
2. Run hermes chat -v -q "run date in terminal"
3. Verify the tool list is not empty and terminal tools work

[isheng-eqi]

Branch contaminated — rebuilding with clean base from upstream/main.