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

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 |
+| [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 |
 | [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 |

decisions/perception.md

@@ -371,6 +371,30 @@ How the player observes and interacts with the world: camera, fog, line-of-sight
 - **Raised by:** Tyre (architecture review, #523)
 - **Dissent:** None
 
+### D-078: Overheard NPC conversation — passive dialogue panel with occlusion filter
+- **Date:** 2026-02-19
+- **Decision:** NPC-to-NPC conversations overheard by the player are displayed in the **dialogue panel in passive mode** (read-only, no response options). An **occlusion filter** degrades displayed text based on distance, ambient noise, and player effort (ListeningFocus stance). Monologue remains a separate channel — it reacts to overheard content via the `witness_interaction` trigger but does not carry conversation text itself.
+- **Passive panel behavior:**
+  - Same D-061 dialogue box, but read-only — no response options rendered.
+  - Shows speaker name and intended target (e.g. "Kael → Mira").
+  - Visually distinguished from interactive dialogue (dimmed border or header treatment — exact style TBD by Araminta).
+  - Walking out of earshot dismisses the panel naturally.
+- **Occlusion filter — server-authoritative:**
+  - Occlusion is computed **on the server**. The server rolls per-word visibility based on distance, ambient noise, and ListeningFocus stance, then sends pre-occluded text to the client with `...` replacing dropped words. The client renders exactly what it receives — no client-side probability logic.
+  - Per-word visibility is a **probability**, not a deterministic cutoff. Each word is independently rolled — same distance, same conversation can yield different fragments across playthroughs.
+  - **Close / clear:** High probability per word — most or all text arrives intact, speaker names shown.
+  - **Moderate distance / some noise:** Medium probability — words arrive as `...`, speaker names visible. The player may or may not catch the crucial word.
+  - **Far / noisy zone:** Low probability — speaker indicators only, few or no readable words. Audio murmur still plays per D-072.
+  - **ListeningFocus stance:** Shifts probability curve upward — improves word visibility at current distance.
+  - **Multiplayer-readiness:** Each observer gets their own occluded version computed from their specific distance/noise/stance. Seedable RNG per tick ensures deterministic replay (D-010).
+  - **Design intent:** Stochastic word-drop means the player can never be certain they got the full picture from eavesdropping alone. This pushes them toward direct conversation to confirm — where they must reveal something about what they know. The information asymmetry loop closes on itself.
+- **Dual-channel principle:** Dialogue panel = what you hear. Monologue = what you think about it. The `witness_interaction` monologue trigger fires after overheard content is displayed, producing the character's internal reaction ("She's lying to him", "So they do know about the cargo"). These are separate UI elements with separate content pipelines.
+- **Content pipeline:** Copy team authors NPC-to-NPC dialogue lines once at full fidelity. The server applies occlusion degradation before sending to the client. No need to author multiple fidelity versions.
+- **Rationale:** Keeps monologue as a clean internal response system — thoughts only, never quoted speech. The dialogue panel already exists for player-NPC interaction; reusing it in passive mode for overheard conversation avoids a new UI element. The occlusion filter makes proximity and attention mechanically meaningful without gating content behind binary thresholds.
+- **Cross-reference:** Dialogue box ([D-061](#d-061-dialogue-box--bottom-screen-max-20-height-no-portraits)), eavesdropping ([D-071](#d-071-no-ambient-dip-for-eavesdropping--listeningfocus-boost)), conversation murmur ([D-072](#d-072-universal-event-driven-conversation-murmur)), monologue system ([D-016](#d-016-internal-monologue-as-core-perceptionatmosphere-system)), knowledge confidence ([D-041](architecture.md#d-041-knowledge-graph-data-model))
+- **Raised by:** Lead (passive panel directive, occlusion filter, monologue separation)
+- **Dissent:** None
+
 ---
 
-*31 decisions. Last updated: 2026-02-19 (D-077: OQ-09 resolved — zone temperature memory server-tracked)*
+*32 decisions. Last updated: 2026-02-19 (D-078: overheard NPC conversation — passive dialogue panel with occlusion filter)*