feat: ✨ spectrafit new-config should emit v2 TOML (not v1 JSON)

[Anselmoo]

Problem

spectrafit new-config -m voigt -n 3 was emitting banned v1 JSON format:

{"fitting": {"peaks": {"1": {...}}}}

The v1 format is hard-rejected by UnifiedFittingConfig since Phase 10.

Solution (implemented in commit 2d6fa967 + be12c14a)

• _PARAM_DEFAULTS: dict[str, dict] → dict[str, FitParameter]
• _build_component() returns Component (Pydantic model, not raw dict)
• _build_config() emits v2 format: {"components": [...], "minimizer": {...}}
• Default output format changed from JSON to TOML
• Removed dead try/except ImportError for tomli_w (it is a hard dep)
• spectrafit init now writes spectrafit.toml project meta file

Verification

uv run spectrafit new-config -m voigt -n 3
# → produces valid [[components]] TOML accepted by UnifiedFittingConfig

Tests: 36 golden-table assertions in tests/unit/test_new_config.py, v2 format check in tests/unit/test_init_command.py.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.