CodexAIModelCatalog: Fix sort comparator for app hang

[sentry]

This PR addresses an app hang issue (REPOPROMPT-J0) caused by a Strict Weak Ordering violation in the sort comparator within CodexAIModelCatalog.swift.

Previously, the options.sorted closure in CodexAIModelCatalog.swift checked for leftBase == rightBase before evaluating lhs.isDefault != rhs.isDefault. This ordering could create a sorting cycle (A < B, B < C, C < A) under specific conditions: when two items shared the same base but differed in their isDefault flag, and a third item had a different base. This cycle caused Swift's sort function to enter a pathological state, leading to excessive reallocations and a main thread app hang of 2000ms or more.

The fix involves reordering the comparator closure to prioritize the isDefault check. The condition if lhs.isDefault != rhs.isDefault { return lhs.isDefault && !rhs.isDefault } is now the very first check, making isDefault the primary sort key. This ensures a valid total order, preventing the sorting cycle and resolving the app hang.

Fixes REPOPROMPT-J0

[morluto]

Audit disposition — fix direction is correct; rebase and prove the comparator contract (2026-08-14)

Making isDefault the primary key removes the described cycle created by applying it only across different base IDs. The narrow code change is directionally correct.

Before merge, add property-style tests for irreflexivity, antisymmetry, and transitivity across generated option triples, plus a deterministic final tie-breaker when localized display names compare equal. Resolve the current integration/CI failure and rerun on the exact final head. I would retain this fix rather than close it.

[morluto]

Deep-review assessment — 2026-08-14

Disposition: logically correct fix; add comparator-law coverage and rerun current CI. Making isDefault the primary key removes the described cycle between same-base and different-base options. The one-line ordering change is preferable to trying to patch individual model combinations.

Please add property/table tests for irreflexivity, antisymmetry, and transitivity across default/non-default, same/different base, effort ranks, and equal localized display names. Add a stable final tie-break such as normalized ID when localized comparison is .orderedSame, so distinct options do not remain unordered. The reviewed exact-head run also had an unrelated compile/test integration failure; rebase and require green current-head CI before merge.