research: Astra pass 2, whole generation chain cost map (read-only)

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

Standalone/Research/WorldAssemblerM3/Astra1/BRIEF-pass2.md

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+Thank you, that was a strong first pass. Your scope warning about L76 was right and important. I need to correct my
+brief: "about 75% of field time is the passage composer" was **wrong**.
+- L76's term profiler covered only about 6.0M legacy samples for FI (5.6M for TN).
+- L73 counts about 52M density calls per FI or TN whole view: 512 LOD0 tiles × 44,121, 448 LOD1 × 43,322, and so
+  on.
+- The measured passage/support cost is about 6.5 of FI's ~40 field worker-seconds (~15%), not 75%. Roughly
+  30 worker-seconds of field time is not attributed to any term we've measured.
+
+Your gain arithmetic for recommendation 1 inherited that error. Please redo it.
+
+## Deeper pass (you now have more reasoning budget)
+
+Examine **the whole generation chain**, end to end, for one cold whole view on the legacy FI/TN path. For each
+stage, say what it does, how often it runs, what it costs per call (from code structure and the measured numbers),
+and whether its work is necessary:
+- world/plan resolution;
+- tile key selection;
+- `ClassifyBoxDetailed`;
+- the dispatch into `AnalyticDensityAt` (and whatever runs for the ~46M calls the term profiler did not see);
+- the composer;
+- grid fill;
+- MC;
+- normals;
+- skirts;
+- ground/cap refinement;
+- payload;
+- Unreal publication.
+
+The central question: **where do the unattributed ~30 worker-seconds most plausibly go?** For example:
+- a different evaluation path the profiler doesn't instrument;
+- per-call overhead outside the timed terms (dispatch, stratum lookup, virtual calls, allocation, cache misses);
+- border/halo samples evaluated twice;
+- normals sampling the field again;
+- duplicated work between neighbouring tiles or LODs.
+
+Give file:line for each. Then name the cheapest measurement that would confirm your top explanation, so the next
+implementation round can verify it first.
+
+Then **revise your ranked recommendations** in the light of the whole chain. Keep what still holds and drop what
+doesn't. Add anything the chain review reveals.
+
+Same rules as before:
+- read-only;
+- no edits anywhere, including temp files;
+- web allowed;
+- labels [CODE]/[MEASURED]/[PRIOR ART]/[INFERENCE].
+- At most ~3,500 words.
+- **Lead with the stage-by-stage cost map**, then the revised ranking.