Add tracer-aware post-processing for linked CO2/O2 RHIME inversions

[brendan-m-murphy]

Goal

Emit clear species/tracer- and sector-aware outputs from linked CO2/O2 inversions.

Tasks

• Preserve concentration outputs by species/tracer.
• Preserve sector-specific and total flux diagnostics.
• Include oxidation-ratio metadata and sign conventions in output provenance.
• Decide whether PARIS outputs are written per species/tracer or as a combined diagnostic bundle.

Acceptance criteria

• Outputs distinguish species/tracer, sector, and total dimensions.
• CO2 and O2 concentration outputs can be generated from one linked inversion.
• Output metadata records conversion factors and sign conventions.