feat(audio): add weapon aim lock and stance change audio assets for #440

Delivers final 2/6 interaction UI audio assets, completing ticket #440:
- sfx_weapon_aim_lock.ogg (0.5s, clinical targeting lock tone)
- sfx_stance_change.ogg (0.35s, soft mechanical stance toggle click)

Both insert-tech aesthetic, UI Sounds bus, non-positional. Generated
via Stable Audio Open, trimmed, LUFS-normalized, converted to ogg.
Updated docs/assets/audio/ui.md with UI-007 and UI-008 entries.

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

docs/assets/audio/ui.md

@@ -17,6 +17,8 @@ Interface sounds triggered by player interaction, insert systems, and cognitive
 | UI-004 | `weapon_aim.ogg` | draft | UI Sounds | SAO | 100-150ms | Harder click/lock for weapon aim state. Mechanical, deliberate. SKETCH ONLY — no weapons in Sprint 7. Needs trim (#453). | S7 #440 |
 | UI-005 | `sfx_monologue_chime.ogg` | draft | UI Sounds | SAO | 500-1000ms | PLACEHOLDER. Soft crystalline tone, neural lattice surfacing a thought. Quiet, non-intrusive. Redo in next audio sprint (#453). See design brief below. | S7 #440 |
 | UI-006 | `sfx_monologue_chime_urgent.ogg` | draft | UI Sounds | SAO | 500-1000ms | PLACEHOLDER. Sharper variant for contradiction/anomaly. Brighter, more insistent. Redo in next audio sprint (#453). See design brief below. | S7 #440 |
+| UI-007 | `sfx_weapon_aim_lock.ogg` | draft | UI Sounds | SAO | 300-500ms | Sharp targeting lock-on confirmation for weapon aim. Clinical/dangerous, harder than general entity lock. Descending digital sweep with metallic precision click. | S8 #440 |
+| UI-008 | `sfx_stance_change.ogg` | draft | UI Sounds | SAO | 200-400ms | Soft mechanical mode-switch click for stance toggle (Walk/Sprint/Careful/Crouch). Subtle digital detent, nearly subliminal. Fires frequently — fatigue-safe. | S8 #440 |
 
 ## Mix Specs (not audio files)
 
@@ -46,6 +48,23 @@ These are AudioBus parameter changes, documented in `docs/audio/dialogue-ambient
 - **Integration:** Cognitive delay onset event → AudioManager.play_ui("fog_recognition")
 - **Cross-reference:** D-060 (cognitive delay), D-018 (three-range sound, medium range)
 
+### UI-007: sfx_weapon_aim_lock
+- **Sonic family:** insert-tech
+- **Frequency range:** 1-3kHz primary
+- **Design principle:** "Crosshair snapping to bone." Clinical confirmation that the weapon system has acquired a target. Harder and more aggressive than cursor_entity_lock — this is the weapon variant. Still UI feedback, not a combat sound. Should not startle.
+- **Generation:** SAO 5s generation, trimmed to best 0.5s transient. Insert-tech prefix + UI template. CFG 8, 100 steps.
+- **Integration:** cursor_state_machine.gd weapon_aim_lock signal → AudioManager.play_ui("sfx_weapon_aim_lock")
+- **Cross-reference:** D-056 (cursor states), weapon_aim.ogg (aim enter, different from lock)
+
+### UI-008: sfx_stance_change
+- **Sonic family:** insert-tech
+- **Frequency range:** 1-2kHz primary
+- **Design principle:** "A precision dial clicking one notch." Subtle neural insert feedback on stance toggle. Player may toggle stances many times while positioning — must be short, pleasant, fatigue-safe. No long tails, no reverb. Nearly subliminal.
+- **Generation:** SAO 5s generation, trimmed to best 0.35s transient. Insert-tech prefix + UI template. CFG 8, 100 steps.
+- **Debouncing:** AudioManager should enforce 150ms cooldown (rapid stance toggling).
+- **Integration:** stance_indicator.gd stance_changed signal → AudioManager.play_ui("sfx_stance_change")
+- **Cross-reference:** D-048 (neural insert feedback aesthetic), D-053 (movement stances)
+
 ### UI-005 / UI-006: Monologue Chime Design Brief (PLACEHOLDER)
 
 **Target emotional register for Sprint 8 redo:**