docs(D288): promote D171 (Silo stray triangle) with user-reproduced, visually-documented repro

User reported a stray triangle during the Silo missile-shaft camera
pan (previously D171, parked since M-34 as "observed, not
investigated"). Reproduced headlessly, precisely bounded to frames
~562-741 of a bare -level_20 boot: a large, flat-shaded, untextured
brown triangle (uniform RGB(83,62,44)) grows then shrinks across the
pan, consistent with a real world-space triangle mis-transformed near
the camera plane rather than a HUD element or garbage vertex-color
read. Points at the D106/D233 near-plane/w-clip neighborhood in
port/fast3d/gfx_pc.cpp, not yet confirmed at the code level. Evidence
saved to docs/img/bugs/. Also noted: foreground `timeout N ...` launches
of the exe from this session's Bash tool produce zero GE_PCDUMP output;
backgrounding the launch works reliably -- worth remembering next time.

Claude-Session: https://claude.ai/code/session_01KwZViAFaXua3PKgHHjNgvi

docs/dev/GRAPHICS-BACKLOG.md

@@ -17,7 +17,7 @@ once the game is playable start-to-finish without crashes.
 | **D148** | Level-end cinematics don't play. Dam: hitting the exit trigger should show Bond rappelling down the dam (the bungee jump); instead it cuts straight to the mission-complete report. **Broader (M-49 full playthrough): cutscenes are buggy in many places across the game**, not just the Dam ending — the user reports frequent cutscene glitches (skipped, wrong camera, misplaced/hovering actors, timing). Treat D148/D160 as the tracking entry for the whole cutscene-reliability problem, not just Dam. | Scripted cutscene / cinematic-camera + Bond rappel anim. Found M-27 during the first full Dam→Facility playthrough. Progression is unaffected — the report and next briefing load fine. The widespread nature (M-49) points at a systemic cause: the propDef/`sizepropdef` stride desync (D122/D132 family) that misreads `CutsceneRecord` lookups, and/or D75 anim-model + D173 actor-position bugs showing up wherever a cutscene puts a character on screen, and/or the D155/D156/D193 timing family driving cutscene camera/anim pacing. **M-31 (§F D160):** static-traced the Dam end ailists (`ai_24`→`ai_17`, `camera_switch`→`CutsceneRecord` type-46 lookup). Diagnostic `GE_D160=1` shipped (`c95713f5`) — user runs Dam to the exit with it set; the trace pins whether the cutscene AI runs, and whether the propDef-index walk (D122/D132 family) hands `camera_switch` a bogus cutscene record. Leading hypothesis: propDef `sizepropdef` stride desync (medium confidence), not D75 anim-model. **M-87 user playtest:** Bond floating/hover cutscene glitch (D173) still present; new specific instance — **Bond spins in circles in some cutscenes**, named example the end-of-Cradle Trevelyan-falls cutscene. Likely the same actor-position/anim-root cause manifesting as bad rotation instead of bad height. |
 | ~~**D149**~~ | ~~Front-end MISSION COMPLETE / mode-select 3D models (dossier, wallets) render as garbled full-screen geometry or not at all.~~ | **CLOSED — user-verified fixed (M-87 playtest).** No longer reproduces; presumably fixed as a side effect of other front-end/D75-family work since M-49. D75 family. §F D146. |
 | **D170** | Named-NPC "flee" scripted behavior looks wrong on PC: on Silo, Ourumov breaks into a full run the instant he alerts ("Ourumov: Kill him!") rather than the N64 walk/retreat; developer reports Trevelyan behaves the same way on Cradle. **M-49 full playthrough: escalated — Cradle (`-level_51`) is "bugged out completely" from Trevelyan's behavior; the final level's scripted progression breaks. Now folded into / superseded by §F D193 (NPC AI locomotion too slow).** | **Observed, not investigated** (M-34, from a Silo playtest capture; user bug report — no fix wanted yet). Could be a genuine ailist / `chrTick` divergence, OR the D155/D156 wall-clock `deltaFrames` locomotion-anim speed-up (a catch-up spike playing the walk cycle at 2–3×). **Verify first:** capture the same beat against N64 reference footage before assuming it diverges — Ourumov may be scripted to flee. If it's real, suspect the frametiming clamp (§F D155/D156) or the Cradle-family AI path (§F D123). |
-| **D171** | Silo missile-shaft: a large translucent grey triangle sweeps across the lower frame while panning down the shaft (~3 s of the capture). Looks like a stray poly / near-plane clip fan, same family as D106 (portal near-plane min>max). | **Observed, not investigated** (M-34, Silo capture). Cosmetic, intermittent, tied to camera angle in the open vertical shaft. |
+| **D171** | Silo missile-shaft: a large triangle sweeps across the frame while panning down the shaft. **Promoted to `docs/dev/findings.md` §F D288 (M-141)** with a user-reproduced, precisely-bounded, visually-documented repro (frames ~562-741 of a bare `-level_20` boot) — read that entry for the current state, not this row. | See D288. |
 | **D172** | Bullet-impact / blood particle spray renders magenta or cyan instead of dark red (visible on guards hit at close range on Silo). | **M-82: ROOT CAUSE FOUND + FIXED (PR #34).** `GE_D172` probe on a user Silo firefight: 40/40 particle tris configure tile 1 = RGBA16 fire @ tmem 392 but fast3d **samples tile 0 (smoke) for both texunits** — `gfx_lod_tile_offset()` returns 0 unconditionally (D107 blurry-ceiling fix; `video.c:225` disables `gfx_detail_textures_enabled`). `G_CC_INTERFERENCE` = `smoke*smoke` → magenta/cyan. Fix: `return rdp.tex_lod ? 0 : i` — only fold to base tile for real LOD/mip draws. (0xB9 + cycle-type were both false trails, ruled out earlier in M-82.) **Owed: in-game eyeball — blood should be dark red.** Detail: `D172-PARTICLE-COLOR-RESEARCH.md`. |
 | ~~**D178**~~ | ~~Objectives not listed correctly on the pre-mission briefing screen (the mission overview shown before starting a level).~~ | **CLOSED — user-verified fixed (M-87 playtest): "main menu text is good now."** No longer reproduces. M-36 triage below kept for reference. **M-36 triage: the objective lines are BLANK, not wrong.** `GE_STARTMENU=10` Dam briefing renders the header fine ("OHMSS / Agent: James Bond / Mission 1: Arkangelsk / Part i: Dam / PRIMARY OBJECTIVES:") then just the bullet "a." with no text and no b/c/d. → **D143/D151 blank-text family** (`langGet()` → NULL → silent blank), *not* a propDef walk / difficulty decode. **Family B** in `docs/dev/M-36-TRIAGE.md` — find which lang bank the front-end briefing flow fails to load. Re-confirm the exact shape in a *real* briefing (the `GE_STARTMENU` boot skips real save state). Close relatives: D151 (watch objective text blank — type-35/23 `text` slot u16→u32 fix, M-28; interactive re-verify was still pending), D143 (briefing/objective text blank via `langGet` NULL), D157 (objective difficulty byte offset — could make difficulty-gated objectives appear/disappear wrongly). The pre-start briefing is a *different surface* from the in-level watch, so D151's fix may not cover it. **Next:** ask user which level + what exactly shows vs expected; compare against `docs/dev/LEVEL-OBJECTIVES.md` (regenerated post-D157); if lines are blank → D143/D151 family (`langGet` NULL guard = silent blank), if wrong objectives listed → propDef type-23 record walk / difficulty decode. |
 | **D175** | In-game stutter / brief hang during normal play — observed opening a door on Runway (mission 3, `-level_35`) and also on Surface. No backtrace captured (gdb attach missed the window; it self-recovered). | **Observed, not investigated** (user QA report). Matches known transient-hang classes rather than looking new: D155 (post-slow-load catch-up spiral — clamped), D156 (anim NaN loop — guarded, prints one-shot stderr diag if it fires), D134 (SP/DP task-done event swallowed — fixed M-22, Runway was an original victim), D147/D152 (audio `s_imLock` steal = ~2 s hiccup). Door-open specifically = new room first visible → one-off texture-import/frame spike (likely benign). **Next:** reproduce under `tools_pc/debug.ps1` with the box idle; check console for the D156 stderr diag; if it recurs, attach gdb mid-hang and pattern-match `bt` (import_texture = benign slow frame; model.c:3131 spin = D156; pthread_mutex_lock on s_imLock = D147/D152). |