test(tunnel): a warning that always means "this is fine" is noise -- demote it

Jahni asked whether a "warning stage" he had been seeing for several sessions
meant something was broken. It did not: the only Warning in that run is the
tunnel test's "[dense fixture] No tile was proved", whose own text explains that
0 proved is the EXPECTED and correct result there -- cull spheres cover the
dense fixture ~3.6x, so no box can be outside all of them. Test passes, density
bit-identical, all coverage non-zero, violations 0, and production defaults
reports 11 proved / 14641 voxels / 0 violations right below it.

But a warning that fires every run and always means "fine" trains the reader to
ignore warnings, and this one quietly worried him across several sessions.

RunTileScan now takes bZeroProvedIsExpected: AddInfo on the dense fixture where
zero is the only possible answer, AddWarning on production defaults where zero
would be a real regression from 11. Same message, severity now carries meaning.

Same defect as the lumped bail counter one layer out: a signal that always says
the same thing measures nothing.

Test-only. Not built.

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

OPSTACK-PROGRESS.md

@@ -4542,3 +4542,27 @@ results from this unbuilt change.
   same `MemoCat == 2` iteration);
 - no protected layout accessor was introduced: the code still uses public
   `GetStrateChunkZBounds`, never `FindSlotIndexForChunkZ`.
+
+## 2026-08-16 (v) — the permanent "warning" was noise, and it cost Jahni several sessions of worry
+
+Jahni: *"[this] have been in a 'warning' stage, is this fine ? is everything fine ?"*
+
+**Everything was fine.** The only `Warning:` in that whole run is the tunnel test's
+`[dense fixture] No tile was proved`, whose own text says *"On the DENSE FIXTURE this is the EXPECTED
+and correct result, not a defect."* The test reports Success; density is bit-identical; every
+coverage number is non-zero; `violations` is 0; and the `[production defaults]` run directly below
+reports **11 proved / 14641 voxels / 0 violations**.
+
+**But a warning that fires on every run and always means "this is fine" is not a warning — it is
+noise that trains the reader to ignore warnings.** It sat there for several sessions and made him
+uneasy about a green suite. That is a real cost, and it came from writing diagnostics for a reader
+who already had the context.
+
+Fixed: `RunTileScan` takes `bZeroProvedIsExpected`. On the **dense fixture** 0 proved is the only
+arithmetically possible answer (cull spheres cover that world ~3.6×) ⇒ `AddInfo`. On **production
+defaults** 0 proved would be a genuine regression from today's 11 ⇒ still `AddWarning`. Same message,
+same information, but the severity now carries meaning.
+
+⇒ **General rule for this project's diagnostics:** if a line cannot distinguish a good run from a bad
+one, it must not be logged at a severity that implies something is wrong. The same defect as the
+lumped bail counter, one layer out: *a signal that always says the same thing measures nothing.*