feat: add Ollama Cloud provider

[Astro-Han]

Summary

• add ollama-cloud as an independent API-key provider backed by the official https://ollama.com/v1 OpenAI-compatible endpoint
• sync the models.dev snapshot, preserve exact Ollama model IDs, and wire deterministic reasoning/tool-call behavior across runtime, Headless, CLI, storage, and Desktop
• keep local ollama unchanged, including its no-auth daemon discovery and local :cloud aliases; reuse the existing monochrome Ollama brand seam without copying assets or notices

Why

PR #907 validated Ollama's local daemon path and exact :cloud aliases, but it intentionally did not add a hosted provider identity, API key, or remote endpoint. Users therefore still could not add Ollama Cloud directly from the provider catalog.

This adds the missing remote identity while keeping local and cloud credentials and connection state independent.

Refs #860.

Scope

Phase 7 is intentionally excluded. No credential migration is performed, and no real provider responses or secrets are recorded.

Verification

• Core: 915/915
• Runtime: 1523 passed, 7 existing skips
• Headless: 893/893
• Storage: 259/259
• CLI: 329/329
• Desktop: 2475/2475
• metadata sync contracts: 22/22
• focused Desktop Ollama Cloud E2E: 1/1
• workspace typecheck
• renderer build and byte-identical third-party notice check
• stale-dist check
• git diff --check
• independent reviewer: 0 P0–P3

The UI change introduces no new visual treatment: Ollama Cloud reuses the governed Ollama mark. The focused Playwright journey verifies catalog visibility, add flow, official endpoint, exact model ID, credential field, and detail surface. Full Desktop E2E is delegated to CI.

Impact

Users can configure Ollama Cloud directly with OLLAMA_API_KEY or the persisted provider credential. Existing local Ollama connections and aliases are unchanged. No migration is required.

Reviewer notes

The deterministic runtime conformance test covers Bearer-authenticated discovery, exact model IDs, Ollama reasoning replay, and a two-stage tool call.

Ready for review

• Verification is complete and the results above are current
• Impact, compatibility, migration, documentation, and release-note needs are addressed
• User-visible UI/UX changes include visual evidence, or Verification explains why it is not applicable