#2654 gatorwalk-factory: validate passes a lifecycle whose graph exploration was truncated

Follow-up from the verification review of swamp-club #2599 (PR #342).

When the structural pass in gatorwalk-factory/extensions/models/_lib/graph.ts reaches the state cap (DEFAULT_MAX_STATES, 100000), analyzeLifecycle reports unreachable-stage, dead-end, gate-never-passes and exit-unreachable as warnings instead of errors. This was a deliberate choice (ADV-3 in the #2599 plan), because those conclusions rest on a partial exploration. But validateHolder (_lib/work_item_ops.ts) only fails on errors. So for a large lifecycle, where the structural state is the stage times the subset of stages entered (roughly 17 or more stages with heavy branching), a real never-passing gate or dead end passes validate with only a warning.

Expected: validate should not report success when it could not finish checking. Options:

• fail validate whenever report.truncated is set, naming the cap and suggesting how to split the lifecycle;
• or keep warnings but make the summary say the check was incomplete and exit non-zero.

Tests: graph_test.ts already has a truncation case (maxStates: 1); add a validate-level case in lifecycle_test.ts.