[upstream #16875] #16875: Cover enum literals, joint rules and ordering in the theme cache pin #301

Three P2 findings from LibreChat-AI#16875 on the resolver output pin in client/src/Providers/__tests__/themeCache.spec.ts, deferred by the owner at head c972bfb.

• Sort the ACCEPTED map by token before hashing, so reordering appearanceValidators does not ask for an unneeded epoch bump: 🧬 test: Pin Built-In Theme Output to the Cache Epoch LibreChat-AI/LibreChat#16875 (comment)
• Include every finite enum literal (for example fieldFillStyle: 'transparent', labelFontWeight: 'inherit') in APPEARANCE_CANDIDATES, so tightening one of them changes the digest: 🧬 test: Pin Built-In Theme Output to the Cache Epoch LibreChat-AI/LibreChat#16875 (comment)
• Add paired fixtures for jointly validated roles (switchWidth with switchHeight), so a tightening that rejects a formerly valid pair changes the digest: 🧬 test: Pin Built-In Theme Output to the Cache Epoch LibreChat-AI/LibreChat#16875 (comment)

The pin is a tripwire for resolver output changes without an epoch bump, not a proof of every validator change. Prefer deriving the candidate set from the validator definitions (enum literals and joint rules) over growing a hand list.