Add ToolRegistry and MCP tools search handler

[binrogithub]

Motivation

• Provide a single authoritative place to declare tool metadata and schemas to avoid duplicated schema definitions across the codebase.
• Make tool discovery deterministic and stable for MCP consumers by producing a canonical catalog view of tools.

Description

• Add hc_agent/core/tool_registry.py with a frozen ToolSpec dataclass and a ToolRegistry class that stores registered tools and exposes a deterministic schema() method.
• Ensure ToolRegistry.schema() sorts tools by name, deep-copies serialized entries, and converts examples to lists to produce stable, JSON-friendly output.
• Add hc_agent/mcp/tools.py with hc_tools_search() that builds the MCP-facing catalog from ToolRegistry.schema() and returns {name, description, risk, input_schema, output_schema, examples} for each tool.
• Create package scaffolding files hc_agent/__init__.py, hc_agent/core/__init__.py, and hc_agent/mcp/__init__.py to expose the new modules.

Testing

• No automated tests were run on these changes.

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Codex Task