Stability checkpoint — switch case pattern fix + matrix validation doc (MR !190) Closes the originally-listed regressions tracked in COMPATIBILITY_MATRIX.md after surgical fix sweep : - catch+try-with-resources patterns (svc 1.0.49 covered) - switch case pattern in ApiExceptionHandler.java:61 (this tag) - Maven java17 profile precedence (svc 1.0.49 covered) - ArchTest kafka method-level + demo controller exclusion (1.0.49) COMPATIBILITY_MATRIX.md updated with validation results from re-triggered compat jobs on pipeline #802. Documents the new structural issues exposed (J17 API overlays for Virtual Threads + List.getLast, SB4+J21 IT infra) — these are pre-existing debt addressed in the next MR (!191).