Release v1.2.0 enrich model capabilities via models.dev

* feat: enrich model capabilities via models.dev and fix provider alias resolution

- Add env var fallback for API key in config hook (OMNIROUTE_API_KEY)
- Generate modelMetadata from enriched models so OpenCode applies capabilities
- Add top-level capability fields (temperature, reasoning, attachment, tool_call, modalities) to provider model output
- Generate reasoning effort variants (low/medium/high) for reasoning models
- Add provider aliases: glmt/glm→zai-coding-plan, kimi-coding/kmc→moonshotai, gh/github→google
- Add subscription fallback: zai-coding-plan→zai, kimi-for-coding→moonshotai
- Add model aliases for naming mismatches (kimi-k2.6-thinking→kimi-k2-thinking)
- Strip reasoning effort variant suffixes (gpt-5.5-xhigh→gpt-5.5) for lookup
- Close 19 of 132 models with 4096 default context limits

* fix: address model metadata review feedback

Preserve user modelMetadata while merging generated capabilities, propagate new capability fields through models.dev and combo paths, and consolidate alias resolution.

* fix: preserve combo attachment metadata

Treat missing attachment capability as unknown instead of false when folding combo model capabilities, while still honoring explicit false values.

* fix: respect explicit attachment false

Avoid falling back to vision support when models.dev or combo metadata explicitly marks attachments unsupported.

* fix: address code review issues from PR #18

- Fix temperature AND-chain bug in calculateLowestCommonCapabilities by tracking hasTemperatureMetadata
- Fix reasoning AND-chain bug in calculateLowestCommonCapabilities by tracking hasReasoningMetadata
- Respect explicit supportsAttachment=false for vision models in toProviderModel
- Add normalized key candidates to getModelLookupCandidates for better alias/variant matching

Addresses feedback from Copilot, Gemini Code Assist, and Kilo Code Bot reviews.

* fix: use nullish coalescing for API key fallback

* fix: add runtime validation for modelMetadata merge

* fix: improve modelMetadata validation coverage

* fix: include modelsDev config in cache key

* refactor: extract splitModelId to eliminate DRY violation

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Co-authored-by: Sebastian Rumpf <alp4d0g007@googlemail.com>