fix: Improve conda error logging and add missing CVs

[lewisjared]

Description

Two sets of fixes:

Improved conda error logging:

• Add CondaCommandError exception that captures stdout/stderr from failed conda commands
• Catch CondaCommandError separately in the executor to log without a stacktrace (the conda output is more useful than the Python traceback)
• Log stderr from failed conda commands (previously only stdout was logged)
• Include execution slug in error messages for easier debugging

Add missing controlled vocabularies:

• Add table_id and global_warming_level dimensions to cv_cmip7_aft.yaml
• Fix facet naming in ClimateAtGlobalWarmingLevels: replace spaces with underscores ("global warming level" -> "global_warming_level") to match CV conventions

Checklist

Please confirm that this pull request has done the following:

• Tests added
• Documentation added (where applicable)
• Changelog item added to changelog/

[codecov]

Codecov Report

❌ Patch coverage is 83.33333% with 3 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
.../climate-ref-core/src/climate_ref_core/executor.py	50.00%	2 Missing ⚠️
...ol/diagnostics/climate_at_global_warming_levels.py	66.66%	0 Missing and 1 partial ⚠️

Flag	Coverage Δ
core	93.11% <86.66%> (-0.01%)	⬇️
providers	91.79% <66.66%> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
...limate-ref-core/src/climate_ref_core/exceptions.py	97.61% <100.00%> (+3.33%)	⬆️
...climate-ref-core/src/climate_ref_core/providers.py	94.08% <100.00%> (+0.02%)	⬆️
...ages/climate-ref/src/climate_ref/executor/local.py	93.82% <ø> (ø)
...ol/diagnostics/climate_at_global_warming_levels.py	94.23% <66.66%> (ø)
.../climate-ref-core/src/climate_ref_core/executor.py	85.71% <50.00%> (-3.42%)	⬇️

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