feat: support configurable model names and restore Skill readback

[RerrentLinden]

Summary

• add optional display-name inputs for the default, quality, fast, and Fable model routes
• keep user-facing display_name values separate from exact upstream model IDs while preserving selectors and role bindings
• authenticate the Science Skill control plane through the current browser URL nonce exchange
• retain the legacy POST /api/auth/nonce endpoint as an explicit compatibility path when the current exchange does not yield an authenticated session
• cover display-name persistence, current and legacy nonce flows, CSRF setup, binding, and readback with regression tests

Root cause

Provider model IDs must remain exact for routing, but slug-like IDs can be filtered when reused as Science-facing display names. The configuration UI previously could not edit display_name independently.

Separately, current Science consumes its control-plane nonce from GET /?nonce=... and returns the session cookies there. CSSwitch still called only the older POST /api/auth/nonce endpoint, which returned 401 invalid bearer token and left the Skill page at “binding readback failed.”

Scope

This PR contains only the configurable model display-name change and the Science nonce/readback compatibility fix. The experimental hybrid Connector/model work is intentionally excluded.

Validation

• cargo test --manifest-path desktop/skill-package/Cargo.toml science::tests::: 12 passed
• cargo test --manifest-path desktop/skill-package/Cargo.toml: 57 passed, 4 ignored
• cargo clippy --manifest-path desktop/skill-package/Cargo.toml --all-targets -- -D warnings
• bash test/run_all.sh --require-release-ready (Python 3.9.6 via a temporary PATH shim): all five layers pass; release-ready green: YES
• npm run tauri build -- --bundles app
• installed App UI smoke check: display names remain separate from upstream IDs; 30 Skills discovered and 29 confirmed attached with “OPERON live readback”