docs: implementation plan + pickup handoff — verbatim retail DrawCells port

Task-by-task plan (TDD pin for the grey regression + per-task visual gates) to replace the
indoor-render approximation with a verbatim PView::DrawCells port, sequenced so Task 2 alone
should kill the grey. Pickup handoff for a fresh session: state, baselines, rules, do-not-relitigate.
Local commit only (not pushed).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

docs/research/2026-06-06-verbatim-drawcells-port-pickup-handoff.md

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+# Pickup Handoff — Verbatim Retail Indoor Render Port (execute in a new session) — 2026-06-06
+
+This session **designed and planned** the verbatim retail `DrawCells` port; the next session
+**executes** it. Spec + plan are committed; render code is NOT yet changed for the port.
+
+## Start here (read in order)
+
+1. **Plan (execute this):** `docs/superpowers/plans/2026-06-06-verbatim-retail-indoor-render-port.md`
+2. **Spec (the why):** `docs/superpowers/specs/2026-06-06-verbatim-retail-indoor-render-port-design.md`
+3. **Retail model:** `docs/research/2026-06-05-retail-pview-indoor-render-pseudocode.md`
+
+## What this fixes (the user's 2-week pain)
+
+Interior walls/floor render **grey** (clear color shows through) and geometry **bleeds**
+between cells; character cut in half on stairs; flap at transitions. Root, located in code:
+`RetailPViewRenderer.cs:52` drops visible cells lacking a `ClipFrameAssembler` slot (grey), and
+`:237` globally disabled the per-cell trim (bleed) because it was wrongly applied to objects
+(half-character). The fix = port retail `PView::DrawCells` (0x5a4840) verbatim: draw **every**
+`OrderedVisibleCells` cell's shell, trimmed **per-slice** via `ClipPlaneSet`→`gl_ClipDistance`;
+objects membership+depth gated, **no** clip. Scope **A+B** (DrawInside + look-in DrawPortal).
+
+## Current tree state
+
+- Branch `claude/thirsty-goldberg-51bb9b`. **Committed this session (local, NOT pushed):** the
+  spec (`eb7b1fa`) and the plan + this handoff.
+- **Uncommitted (dirty) — KEEP, do not revert:** this session's faithful work is the foundation
+  the plan builds on —
+  - `PortalProjection.ProjectToClip` / `ClipToRegion` = homogeneous `GetClip`/`polyClipFinish`
+    (NEW, tested). `PortalVisibilityBuilder` rewired to use them (merged with a concurrent
+    agent's `[pv-trace]` work). These are the membership + clip math; the plan does NOT touch them.
+  - The rest of the dirty render tree (RetailPViewRenderer approximation, ClipFrameAssembler,
+    GameWindow rework, ObjectMeshManager #6, etc.) is the tangle the plan rewrites/deletes.
+- **Baselines (must hold at start):** `dotnet build -c Debug` 0 errors; App.Tests **205/205**;
+  Core.Tests **1331 pass / 4 fail / 1 skip** — the 4 fails are pre-existing Physics door/step-up
+  (`BSPStepUpTests.D4_Airborne…`, two `DoorBugTrajectoryReplay.LiveCompare_*`,
+  `DoorCollisionApparatus…DocumentsBug`), unrelated to render.
+
+## Rules (user-set, this worktree)
+
+PowerShell on Windows; launch logs UTF-16. Do **NOT** branch/worktree, push, `git stash`/`gc`,
+or revert the dirty tree. Build before every launch. **Acceptance is the user's eyes** — do not
+claim a GL task done on a green build; only on the user's visual confirmation (the plan gates each
+GL task on a launch). Live server: ACE `127.0.0.1:9000`, account `testaccount`/`testpassword`,
+char `+Acdream` (spawns at the Holtburg cottage). Graceful-close the client between launches
+(hard-kill leaves the ACE session stuck ~3 min).
+
+## DO NOT re-litigate (evidence-disproven)
+
+- The grey is **shell-sealing / wrong-flood-root**, NOT the portal projection. Do not "harden the
+  w-clip" further — the clip math is already faithful this session. (Two handoffs contradicted on
+  this; the 2026-06-05 shell-sealing handoff + the live visual were right.)
+- If, after every shell draws (per `[render-sig] draw=[…]`), walls are sealed but **untextured**
+  (grey-but-drawn, vs. clear-color grey), that is a **separate surface/texture bug** (HEAD commit
+  notes "interior walls grey") — file it; do not reopen membership/clip.
+
+## Recommended execution
+
+Subagent-driven (a fresh subagent per task, review between) or inline (`executing-plans`). The plan
+is sequenced so **Task 2 alone should make the grey disappear** — verify that with the user before
+continuing; it de-risks the whole effort.
+
+## Copy-paste pickup prompt
+
+```
+Execute the verbatim retail indoor render port in worktree thirsty-goldberg-51bb9b
+(branch claude/thirsty-goldberg-51bb9b). Do NOT branch/worktree, push, git stash/gc, or
+revert the dirty tree. PowerShell; launch logs UTF-16; build before launch; acceptance is the
+user's eyes (gate every GL task on a launch + the user's visual OK).
+
+Read first:
+1) docs/superpowers/plans/2026-06-06-verbatim-retail-indoor-render-port.md  (execute this, task by task)
+2) docs/superpowers/specs/2026-06-06-verbatim-retail-indoor-render-port-design.md
+3) docs/research/2026-06-06-verbatim-drawcells-port-pickup-handoff.md  (state + rules + do-not-relitigate)
+
+Confirm baselines (build 0 errors; App 205/205; Core 1331/4 pre-existing/1), then use
+superpowers:executing-plans (or subagent-driven-development) to implement. Task 2 should make the
+grey disappear — get the user's visual confirmation before continuing. The grey is shell-sealing,
+NOT the projection; the clip math is already faithful — do not harden the w-clip.
+```