feat: add Claude Opus 5 support

[backryun]

What changed

• Add Claude Opus 5 and the verified Claude 5 family catalog entries across Anthropic, Claude, Claude Web, GitHub Copilot, and GHE Copilot.
• Add model specs, pricing, ordering, fallback behavior, Fast Mode support, and provider-specific request handling.
• Align Claude Web streaming, slow-first-byte handling, adaptive thinking, beta flags, and cooldown-aware retries with the current model behavior.
• Centralize the Claude Code client fingerprint and update active UA/version values to 2.1.219 across code, environment defaults, snapshots, tests, and documentation.

Why

The provider catalogs and Claude request paths still assumed earlier Claude generations, while Claude Code identity values were duplicated and had drifted. This prevented consistent Opus 5 routing and produced mismatched behavior between API, web, and Copilot transports.

Impact

OmniRoute can advertise and route Claude Opus 5 through the verified providers with consistent thinking, pricing, fallback, and client identity behavior. Fable 5 remains first in the flagship model ordering.

Validation

• Changed unit tests: 289 passed
• npm run typecheck:core
• npm run check:docs-all
• ESLint on changed source files
• Pre-commit formatting, ESLint, documentation sync, explicit-any budget, and tracked-artifact checks

[backryun]

I tested, everythings works!

++ The GitHub 400 error occurred because I have a Copilot Student subscription. For now, I've included everything that was possible to implement.

[diegosouzapw]

Thanks for this — verified the model ID, context window, and pricing for Claude Opus 5 all match the current official spec, and confirmed there was no existing catalog entry for it on release/v3.8.49, so this fills a real gap rather than duplicating anything.

I ran the full test suite for the touched area in an isolated checkout (331 tests, 0 failures), typecheck:core (clean), ESLint on the changed files (clean, and nice catch removing the two any usages in claudeIdentity.ts along with the now-stale suppression entry), and the docs-sync gate (PASS across all 42 i18n locales). The disabled thinking capped at high effort handling for Opus 5 and the Claude Web thinking_mode: "auto" path both look correct against the documented model behavior.

The Claude Code client-identity version bump (2.1.207 → 2.1.219) bundled in alongside the Opus 5 work makes sense as a coupled change (OAuth identity gating needs the real captured client version), so we're keeping it as-is rather than asking you to split it out.

This is merge-ready as submitted — no changes requested. Thank you for the thorough work, including the new regression tests.

[diegosouzapw]

Merged into release/v3.8.49 — thanks @backryun! Validated via a 26-PR local merge-train + per-file discriminator confirming zero regressions vs the pure release tip. 🙏