Harden OpenRouter metadata and verification

[ITSMERNB]

Summary

Closes #6 by recording and implementing the provider direction: harden the existing OpenRouter adapter before adding a fourth provider.

Changes

• preserve OpenRouter catalog names, context lengths, and supported parameters
• derive tool support from supported_parameters instead of assuming every model supports tools
• add deterministic rich/fallback/catalog-shape tests
• replace the former no-key live-test no-op with an explicit ignored authenticated catalog + streaming completion test
• add scripts/verify-openrouter.ps1 with honest PASS/SKIP reporting
• verify the public catalog schema and configured default/research model IDs without storing credentials
• document the decision and nominate a generic OpenAI-compatible local/server adapter as the likely later expansion

Verification

• OpenRouter deterministic tests: 7 pass, 1 authenticated live test ignored
• public catalog gate: pass; 338 models observed, 272 advertising tool support
• authenticated completion: SKIP because SC_AGENT_OPENROUTER_API_KEY is not present
• full workspace tests: 274 passed, 0 failed, 2 explicit ignored tests
• fmt/check/clippy/release: pass
• public Rust API/package gate: pass
• public beta gate: 16 pass, 0 fail, 1 honest skip
• tracked-file public/secret scan: 126 files, 0 hits

This PR does not add a provider, store a credential, call a paid completion, or claim authenticated OpenRouter verification.