fix: return resource-not-found error code

[sarvesh1327]

Summary

• Return the MCP resource-not-found error code (-32002) when resources/read matches no registered resource or template.
• Add a focused UnknownResourceError path so matched template failures remain generic read failures instead of being reported as missing resources.
• Update interaction requirements and regressions for both missing resources and template failure semantics.

Fixes #1579

Test Plan

• uv run --frozen pytest tests/interaction/mcpserver/test_resources.py -q
• uv run --frozen ruff check src/mcp/server/mcpserver/server.py src/mcp/server/mcpserver/resources/resource_manager.py src/mcp/server/mcpserver/resources/__init__.py src/mcp/types/jsonrpc.py src/mcp/types/__init__.py tests/interaction/mcpserver/test_resources.py tests/interaction/_requirements.py
• uv run --frozen pyright src/mcp/server/mcpserver/server.py src/mcp/server/mcpserver/resources/resource_manager.py tests/interaction/mcpserver/test_resources.py
• git diff --check