Preserve v0 species/reaction properties needed for v1 conversion

[K20shores]

Problem

Converting a v0 (CAMP) config to v1 — or running one through MICM — dropped or omitted several fields the v1 representation needs. Three distinct v0-parser gaps, each surfaced while getting a real v0 music_box config to run on current musica:

1. Diffusion coefficient — parsed onto the species but dropped when v0 places all species into the gas phase (only the name was copied). MICM reads the coefficient from the phase species (e.g. for surface reactions), so any v0 surface-reaction species failed with Diffusion coefficient for species '<name>' is not defined (e.g. GLYOXAL).

2. THIRD_BODY tracer — a CHEM_SPEC with tracer type: THIRD_BODY recorded only the tracer-type string, which the unified type does not carry into v1 serialization (v1 represents a third body via is third body). Species like M silently lost their third-body role on conversion.

3. Reaction gas phase — v0 reactions left gas_phase empty, but the v1 parser requires every reaction to name a non-empty gas phase, so a converted mechanism failed to re-parse with Unknown phase ''.

Fix

In the v0 parser, when building the single gas phase that all v0 species/reactions belong to:

• carry each species' diffusion coefficient onto its PhaseSpecies;
• set is_third_body when the tracer type is THIRD_BODY;
• set every reaction's gas_phase to "gas".

Extends the v0 species and arrhenius unit tests to cover all three. All v0 tests pass.

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