Extract the static model maps (MODEL_MAP, MODEL_FORCED_EFFORT, THINKING_CAPABLE_SLUGS)
and the pure thinking-effort resolvers (isThinkingCapableModel, normalizeThinkingEffort,
resolveThinkingEffort, ResolvedChatGptModel, resolveChatGptModel) verbatim into the pure
leaf chatgpt-web/models.ts. Host imports the two resolvers it uses back.
Host 3205 -> 3076 LOC. Byte-identical bodies (verbatim multiset 120/120), leaf has zero
imports (no cycle). Auth/PoW/session/HTTP dispatch and all module caches untouched.
Adds a split-guard; consumer tests stay green (chatgpt-web 86, chatgpt-web-tools-5240 4,
chatgpt-web-sha3-boringssl-5531 5).
