feat(docs): add D-078 — overheard NPC conversation via passive dialogue panel

Server-authoritative stochastic per-word occlusion filter for NPC-to-NPC
conversations. Dialogue panel in passive mode displays pre-occluded text;
monologue remains a clean internal response system. Indexes updated.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

CLAUDE.md

@@ -35,7 +35,7 @@ db/
 decisions/            # Decision domain files (source of truth)
   README.md           # Domain index and query examples
   architecture.md     # D-008, D-009, D-010, D-012, D-020, D-026, D-030, D-031, D-041, D-042, D-054, D-055, D-066
-  perception.md       # D-011, D-015, D-016, D-017, D-018, D-019, D-033, D-035, D-043-D-049, D-052, D-056-D-061
+  perception.md       # D-011, D-015, D-016, D-017, D-018, D-019, D-033, D-035, D-043-D-049, D-052, D-056-D-061, D-067, D-069-D-072, D-076-D-078
   content.md          # D-023, D-024, D-025, D-028, D-029, D-032, D-034-D-037, D-050, D-062-D-064
   scope.md            # D-001, D-003, D-005, D-006, D-007, D-013, D-014, D-027, D-038, D-039, D-051, D-053, D-065
   process.md          # D-004, D-021, D-022