docs: handoff — add an unattended-run work queue for stage B

Jahni may start a session and leave, then have it shut the PC down. The
successor still cannot build, so the section is about shaping ~680 lines of
mechanical transcription for ONE informative build afterwards rather than
pretending verification is available.

Work queue B1-B5 (roughness / terrace-layerlines-ribbing / overhang-cliff-
scallop-arch / columns-domes-pinch-floorbias / the bNearCaveSurface gate),
one commit per group with the group named in the subject line, since Jahni
reverts by group. Transcribe literally, note anything that looks wrong in
the log and port it as-is anyway — that is how C1 and the MinDivisor split
were both found without breaking anything.

Records the subtlety that lets B precede C: the 13 modifiers read a copy of
the params with the nearest room's op applied, so porting them against
strate-level params is equivalent only while the test's room pool stays
Pit/Chimney-only.

Hard stops: do not flip TunnelNetwork or Underwater on, do not start stage C
(design freedom without feedback), do not start the worm amplitude cap (it
changes the fold contract all 13 tests rest on), do not build or push.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

OPSTACK-HANDOFF.md

@@ -110,6 +110,98 @@ by a test that compares it to the original. Only the ~60 lines of glue are trans
    `CarveOnly` whenever any shaft is within a `Spacing*1.6` halo instead of testing real connector
    capsules. Lost CPU, never a hole.
 
+## ⚠️ IF YOU ARE RUNNING UNATTENDED — read this section before starting
+
+Jahni may start this session and leave, then have you shut the PC down when you're done. If so:
+
+**You cannot build, and nobody will build for you during this run.** Rule #1 still holds absolutely.
+So everything you write stays unverified until he returns — which is exactly the `AUDIT §P3` pattern
+("unverified code on top of unverified code") this refactor has dodged seven times. You cannot avoid
+it while he is away. **What you CAN do is shape the work so a single build afterwards diagnoses it
+cheaply.** That is the whole job of this section.
+
+### The rules that replace "build after each step"
+
+1. **One commit per group below. Never bundle two.** Jahni reverts by group, and a failed build must
+   bisect to a group rather than to 700 lines. Name the group explicitly in the subject line.
+2. **Every commit leaves the tree coherent.** No half-written op, no dangling brace, no factory
+   declared without a definition. Assume the next thing that happens is a compile.
+3. **Transcribe literally. Do not improve anything.** With no test feedback, a "cleanup" is an
+   unfalsifiable guess. Keep the original's operation order, its constants, its `FVector`
+   round-trips, its odd `FMath::Max` floors. If something looks wrong, **write it down in the
+   progress log and port it as-is** — that is how `§C1` and the `MinDivisor` split were both found
+   without breaking anything.
+4. **Update the test in the same commit as the code it covers**, including its coverage counters. Do
+   not leave "I'll add the test after" — after is a build away.
+
+### The work queue, in order. Stop at the first hard stop.
+
+- **B1 — Surface roughness** (`STEP 4b`, ~130 lines). Density-space variant: a *different op* from
+  `FSdfRoughnessMod` (quadratic fade, anti-fill clamp, 4 noise types). See `DECOMPOSITION §1`.
+- **B2 — Terrace · LayerLines · Ribbing** (~150 lines). The three "sedimentary" remaps.
+- **B3 — Overhang · Cliff · Scallop · Arch** (~210 lines).
+- **B4 — Columns · Domes · Pinch · FloorBias** (~190 lines). Columns read `SDFCache.Columns`, so this
+  group needs a Column op in the test's room pool — and the stage-A guard that *errors* on
+  `TotalColumns > 0` must move to this commit, not before it.
+- **B5 — the gate itself.** All of B1–B4 live inside `if (bNearCaveSurface)`, i.e.
+  `Sdf < SDFBlendRadius·3 && Sdf < FLT_MAX`. Decide deliberately whether that is one scoping wrapper
+  or a repeated early-out in each op, write down which and why, and make the test prove a voxel
+  *outside* the gate is untouched.
+
+After each group, extend the test: turn that group's amplitudes ON in `EnableTunnelFeatures`, add a
+coverage counter proving the group actually fired (**not** just that its param is non-zero — see the
+pit/chimney lesson below), and move the op-count assertion.
+
+**⚠️ The one subtlety that lets B happen before C.** Inside `if (bNearCaveSurface)` the original
+*shadows* `Params` with `LocalTerrainParams` — a copy with the nearest room's terrain op applied — and
+**all 13 modifiers read the shadowed copy**. Porting them to read strate-level params is therefore
+equivalent *only while no room carries a detail-type op*. The test's room pool is Pit/Chimney only,
+and `ApplyTo(Pit)` writes just the four pit fields, so the two are identical today. **Keep it that
+way until stage C**: the moment a `Terrace` op enters the pool, the ported group must read the
+per-room value or the equivalence breaks — and that break is the correct signal, not a bug.
+(B4's Column op is safe: `STEP 4d` reads `SDFCache.Columns` from the bake, never the shadowed params.)
+
+### 🛑 HARD STOPS — do not cross these unattended
+
+- **Do NOT flip `TunnelNetwork` or `Underwater` on in `UsesOperatorStackForChunk`.** That points the
+  live world at an unverified path. It waits for a green build, always.
+- **Do NOT start stage C (the per-room op override).** It is the one piece with genuine design
+  freedom (`§2` offers two options and argues for (a)), and design without feedback is where an
+  unattended run does damage. **Instead, if you reach it: write the design up in
+  `OPSTACK-DECOMPOSITION §2` and stop.** A reviewed design is worth more than unreviewed code.
+- **Do NOT start the worm amplitude cap / numeric intervals.** It changes the fold contract that all
+  13 green tests depend on. It deserves a build cycle of its own.
+- **Do NOT build, do not launch the editor, do not push.** Unchanged, and not negotiable.
+
+### If you finish B1–B5 and still have time
+
+Prefer work that is **valuable without a build**, in this order:
+
+1. **Settle `AUDIT §C2`'s suspected item** — does `GetGenerationParams` actually vary within one
+   strate across a Gradient transition? That is answerable by *reading* `GetGenerationParams` and
+   `FStrateGenerationParams::Lerp`. Turn the suspicion into a yes or a no, with the evidence, and
+   correct the audit either way. **This is the highest-value build-free task available.**
+2. **Write the stage-C design** (above) without implementing it.
+3. **Re-read your own B1–B4 diffs against the original**, function by function, as a reviewer rather
+   than an author. On a run with no tests, a second reading is the only oracle you have.
+
+### The commit messages ARE the ledger
+
+**Jahni's words: "just commit with explicit name what changed, I'll revert if needed."** So there is
+no separate bookkeeping — the commit history is the record, and it has one job: let him revert a
+single group without touching the others.
+
+That makes the subject line load-bearing. Name the group and the scope, not the intent:
+
+```
+feat(opstack B2): port Terrace, LayerLines, Ribbing detail modifiers
+feat(opstack B4): port Columns, Domes, Pinch, FloorBias + column op in the test pool
+```
+
+Body: what was transcribed, anything that looked wrong and was ported as-is anyway, and what breaks
+first if the group is wrong. One group per commit — that rule exists *because* of the revert
+workflow, so it is the one thing not to bend.
+
 ## Hard rules that prevent real bugs
 
 - **Density sign:** negative = solid at the mesher. Inside the op stack the convention is INTERNAL