docs(decisions): register D-084 insert icon system — custom SVG, no icon font

Insert overlay uses custom SVG icons instead of an icon font. No
available font matches the neural lattice visual language. Custom
SVGs respond to lattice_profile weight parameter and maintain visual
coherence with existing geometric primitives.

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

decisions/README.md

@@ -11,7 +11,7 @@ Cross-domain decisions live in one file with cross-reference notes in related fi
 | File | Domain | Decisions |
 |------|--------|-----------|
 | [architecture.md](architecture.md) | Technical foundation | 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, D-068, D-073 |
-| [perception.md](perception.md) | Player observation | D-011, D-015, D-016, D-017, D-018, D-019, D-033, D-035, D-043, D-044, D-045, D-046, D-047, D-048, D-049, D-052, D-056, D-057, D-058, D-059, D-060, D-061, D-067, D-069, D-070, D-071, D-072, D-076, D-077, D-078 |
+| [perception.md](perception.md) | Player observation | D-011, D-015, D-016, D-017, D-018, D-019, D-033, D-035, D-043, D-044, D-045, D-046, D-047, D-048, D-049, D-052, D-056, D-057, D-058, D-059, D-060, D-061, D-067, D-069, D-070, D-071, D-072, D-076, D-077, D-078, D-084 |
 | [content.md](content.md) | NPC, dialogue, templates | D-023, D-024, D-025, D-028, D-029, D-032, D-034, D-035, D-036, D-037, D-050, D-062, D-063, D-064, D-074 |
 | [scope.md](scope.md) | Game concept, prototype | 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](process.md) | Team, workflow | D-004, D-021, D-022, D-040 |