Check idata dims/coords consistency before sampling (fixes #7891)

[atheendre130505]

Description

This PR implements validation to check idata dimensions and coordinates consistency before sampling begins, addressing issue #7891.

Problem

Previously, sampling would fail with unclear error messages when idata had inconsistent dims/coords with the model. This made debugging difficult.

Solution

Added early validation that:

• Checks dims/coords in idata before sampling starts
• Provides clear, actionable error messages for mismatches
• Prevents confusing failures deep in the sampling process

Testing

• All existing tests pass locally
• Manual testing confirms expected error behavior for dimension mismatches

Related Issue

Fixes #7891

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📚 Documentation preview 📚: https://pymc--7949.org.readthedocs.build/en/7949/