Codex discovery under-reports the gpt-5.6 sol/terra/luna window: some
accounts omit `context_window`, others actively return 272000. The #5707
`?? fallback` only fired on absence, so an actively-reported 272000 passed
through and `preferDiscoveryLimit` overwrote the bundled 372K pin at
runtime, dropping compaction from 279000 to 204000 tokens.
Treat GPT_5_6_CONTEXT_WINDOW as a floor for these SKUs via Math.max so
neither omission nor active under-report regresses the real capacity;
other models keep honoring the reported value. Corrected the stale
"omits" comments in codex.ts and generated-policies.ts.
Fixes#6259
roboomp
930bb33f4a