proto: first liminal fixtures - flat field + monolith, periodic hills, raised road in fog (L141)

Standalone only: fixtures, liminal_road_override (fillDais), --audit-liminal-road-walk, capture-only distance fog.
Road 65 m x 6 m, 22 m up, capsule walk 127/127. Owner hashes unchanged (v227), fast tier, Clang/GCC green.
Hills repeat every 80 m but the capture reaches 56 m, so only one rise shows. Also R48 (who owns the tunnel mouth):
recommends a bounded joint plan of passage ports and layer landing candidates.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016dhxM43dnWvUu2B5Ph1iG1

Standalone/Research/WorldAssemblerM3/Research48/PROMPT.md

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+# VoxelForge — research R48 (read-only): who owns the tunnel mouth?
+
+You are a researcher. **Read only:** don't edit, create or delete any file, and don't build, run or test anything.
+Read code, reports and design docs. Be thorough, verify by hand, and mark each claim [CODE] file:line, [MEASURED]
+report, or [INFERENCE]. This checkout (`Saved/Linux/r48-tree`) is branch `wip/l134-cave-planner` at `4f93f3f`.
+
+## The problem
+
+Inter-strate passages (tunnels between layers) are planned first, and each layer's content is planned afterwards
+around their fixed mouths and tubes.
+- **Tunnel Network** (L134–L138) works, because caves are carved into rock and can bend to the mouths.
+- **Vertical Shafts** (L139): 15/16 seeds pass; seed 2 fails the shell and seams at the arrival mouth. Three local
+  geometry fixes failed.
+- **Floating Islands** (L133 twice, then L140): 0/16 seeds pass.
+  - In 14 of 16 seeds, no island arrangement clears the fixed tubes and reaches both mouth heights.
+  - One seed has a composed collision.
+  - Wall ripple is 6–7 cm against the 3.5 cm limit on the passages.
+
+Read the L133, L139 and L140 reports and patches in `Standalone/Research/WorldAssemblerM3/`.
+
+## Questions
+
+1. Where and in what order are passages and layer contents planned (adapter, `ResolvedLayoutInternal.h`, the
+   passage planner, the island and cave planners)? What does each stage fix that later stages must obey?
+2. Which designs would make mouths solvable by construction for every layer type? For example:
+   - **content first:** the layer plans its landing spots, and passages are routed to target them;
+   - **negotiated:** passages reserve a mouth landing region, and every layer planner must provide support there,
+     a "landing pad" contract;
+   - **a joint plan:** a corridor and the island anchors are solved together.
+   For each: what changes, the risks (determinism, the existing audits, the passage smoothness/ripple work), and the
+   size.
+3. Why does ripple fail at 6–7 cm on the upper passages with native islands (and in L67)? Is it the passage, or the
+   host field under it?
+4. Recommend one design, with steps and the evidence that would prove or kill it.
+
+Write plain Markdown, ≤ ~1,200 words.