Auto-combo transparency + budget controls: the engine's budgetCap enforcement
always degraded to the globally cheapest candidate when every candidate
exceeded the cap - silently overspending instead of respecting the cap.
- engine.ts: budgetFallback "cheapest" (default, legacy) | "strict"
(BudgetExceededError when no candidate fits budgetCap)
- requestControls.ts: X-OmniRoute-Budget-Fallback header +
resolveRequestAutoControls() consolidating mode/budget/fallback parsing
- resolveAutoStrategy.ts / autoConfig.ts: thread combo-level
config.budgetFallback and catch BudgetExceededError into an HTTP 402
- chat.ts: switch to the consolidated resolveRequestAutoControls() helper
(net line reduction, stays under the frozen file-size baseline)
Regression guard: tests/unit/auto-combo-budget-fallback-3470.test.ts
Register 8 new advanced MCP tools (simulate_route, set_budget_guard,
set_resilience_profile, test_combo, get_provider_metrics,
best_combo_for_task, explain_route, get_session_snapshot) with their
handler implementations. Add A2A smart routing skill that routes
prompts through the OmniRoute pipeline with routing explanation,
cost envelope, and resilience trace metadata.
