Make sure that the imported data is numeric

[mattfidler]

Closes #208

When filtering based on NONMEM input information, sometimes the data
frame is still character values instead of numeric values.

This pull request should fix that.

[Copilot]

Pull Request Overview

This PR addresses issue #208 by ensuring that imported NONMEM data is converted to numeric types when appropriate. The problem occurred when filtering based on NONMEM input information resulted in character values instead of numeric values.

Key Changes:

• Added numeric conversion logic to handle character data that represents numeric values
• Implemented comprehensive NA/missing value handling during conversion
• Added test coverage for the numeric import functionality

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

File	Description
R/readInNonmemInput.R	Core fix: Added conversion loop to transform character columns to numeric when possible, with special handling for various NA representations
tests/testthat/test-import-numeric.R	Added test case to verify numeric import with data filtering using IGNORE clauses
NEWS.md	Documented the fix for issue #208
DESCRIPTION	Bumped version to development version 0.1.8.9000

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