fix(coding-agent): naturally sort both model selectors

[Omzig]

Summary

Make both interactive model selectors easier to navigate when providers expose context-window variants.

What changed

• Share a natural model-ID comparator between /model and /scoped-models.

• Sort model IDs case-insensitively with numeric awareness.

• Keep canonical model IDs before their context aliases.

• Sort numeric context aliases by actual size, so variants appear as:

  gpt-5.6-luna
gpt-5.6-luna@200k
gpt-5.6-luna@1m

• Preserve the explicit order of enabled models in /scoped-models; Alt+Up/Alt+Down still controls that order.

• Sort the remaining available catalog predictably in /scoped-models.

• Apply the same provider-and-model ordering to the all-model /model selector.

• Preserve existing search and enable/disable behavior.

The comparator is provider-agnostic and applies to any model IDs using numeric @...k or @...m context suffixes, not only GitHub Copilot models.

Why

GitHub Copilot discovery now exposes multiple context-tier aliases for many models. The previous selectors displayed newly discovered models in provider/catalog order, and lexical ordering placed @1m before @200k. The two selectors could also present different orders, making variants difficult to find and compare.

Validation

• Added regression coverage for /scoped-models ordering and /model all-model ordering.
• Targeted coding-agent tests: 5 passed.
• npm run check: passed.
• Full ./test.sh was attempted; unrelated Windows/environment failures occurred in workspace startup, Unix socket, path-normalization, provider setup, and missing built workspace artifact tests.

Fixes #7693

[github-actions]

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