889294a5fd
When users configure agents.sisyphus-junior.model, category sessions should use that model without falling back to hardcoded AGENT_MODEL_REQUIREMENTS. Two leaks existed: 1. Launch-time: category-resolver.ts did not check overrideModel when deciding whether to use the hardcoded fallbackChain. Fixed by adding overrideModel to the suppression condition. 2. Runtime retry: model-fallback hook.ts treated undefined fallbackChain (from setSessionFallbackChain(id, undefined)) as 'no override' and fell through to AGENT_MODEL_REQUIREMENTS on session.error/status retry. Fixed by storing explicit empty array and checking .has() instead of truthiness. Tests added: - hook.test.ts: explicit empty session fallback suppresses agent chain - event.model-fallback-2941.test.ts: session.error does not arm retry - category-resolver.test.ts: overrideModel suppresses fallbackChain - tools.test.ts: sisyphusJuniorModel override assertion