Fix Conda build failure due to missing conda-build in GitHub Actions environment

[harryswift01]

Summary

This PR addresses a GitHub Actions CI issue where Conda tooling (e.g. conda-build) is installed but not reliably available during workflow execution due to inconsistent environment activation across steps.

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Changes

Standardised Conda environment activation in CI:

• Ensured Conda environments are consistently activated across all workflow steps
• Configured setup-miniconda to reliably activate the intended environment (e.g. base or target env)
• Enabled automatic environment activation to prevent step-to-step state loss
• Added basic sanity checks (e.g. conda list, conda build --help) to verify Conda tooling availability during CI runs
• Improved reproducibility of Conda-based builds in GitHub Actions

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Impact

• Improves reliability of Conda-based CI workflows across repositories
• Eliminates intermittent failures caused by environment activation inconsistencies
• Aligns CI behaviour more closely with local development environments
• Makes Conda setup issues easier to detect and debug early in pipeline execution
• Provides a standard pattern that can be reused across multiple repositories in the organisation

[jimboid]

Looks like this fixes the issue. Not sure why it would be intermittent though but the fix here makes sense.