docs: launch-options reference + the test that keeps it honest

The client reads 161 ACDREAM_* environment variables across 79 files. Only
about 25 were written down, and the audit found the documentation drifting
in both directions: CLAUDE.md still advertised ACDREAM_RUN_SKILL /
ACDREAM_JUMP_SKILL (deleted; skills are server-authoritative now, and the
jump fallback is 300, not the documented 200), while flags with real
side effects had no description at all.

docs/launch-options.md documents every one by lifecycle — production,
command line, measurement, automation, permanent diagnostics, temporary
probes, deprecated, retired — with a mandatory side-effects column. That
column is the point: #432 cost three days of taxed measurements because
ACDREAM_AUTOMATION_ARTIFACT_DIR reads like an output path and also builds
a per-frame diagnostics referee, and ACDREAM_STREAM_RADIUS silently
measures a streaming window production never uses. Rows now say so. Other
surprises the audit surfaced and recorded: ACDREAM_DUMP_SCENERY_Z swaps in
a duplicate scenery-placement path rather than only logging,
ACDREAM_PROBE_VIS silently also enables ACDREAM_PROBE_ENVCELL, and
ACDREAM_DUMP_ENTITY's id list doubles as an unrelated probe's watchlist.

LaunchOptionsDocumentationTests enforces it, because a hand-maintained list
of 161 flags is stale within a week: an undocumented flag fails, and so
does a documented row whose read site was deleted. It scans string literals
rather than GetEnvironmentVariable call shapes — the startup path reads
through an injected delegate, so a call-shaped pattern silently missed
ACDREAM_LIVE, ACDREAM_PAK_PATH and every other production flag. A third
test freezes per-file direct-read debt by exact count (20 files outside the
owner classes), so structure rules 4 and 5 can be paid down but not
regressed.

CLAUDE.md's 94-line env-var section becomes a 16-line pointer, and its
stale test-character paragraph is corrected.

Also fixed, all doc-vs-code mismatches the audit proved:
- RenderingDiagnostics.FrameProfEnabled described a GPU-query self-disable
  that Campaign V slice V11 deleted.
- Two comments named ACDREAM_RENDER_BACKEND as a live co-requisite; it died
  with the OpenGL backend.
- EnvCellRenderer.CollectCellAuditLines and its ACDREAM_A8_AUDIT doc: the
  method had no caller anywhere and its documented caller never existed.

Filed rather than fixed, to keep this a documentation change: #434 (the
DebugPanel/DebugVM surface is never constructed, so ~40 "runtime-toggleable"
comments are false and 35 env reads are unreachable) and #435 (17 temporary
probes outlived their closed investigations; 14 more name no owner).

Full hermetic suite 12,202 passed / 0 failed.

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

src/AcDream.App/RuntimeOptions.cs

@@ -215,11 +215,12 @@ public sealed record RuntimeOptions(
             // can be exercised on hardware that actually supports everything.
             VulkanForcedUnsupportedFeature:
                 NullIfEmpty(env("ACDREAM_VULKAN_FORCE_UNSUPPORTED")),
-            // Campaign V slice V6h: with ACDREAM_RENDER_BACKEND=vulkan, run the
-            // V5/V6c bring-up harness — capability gate plus the synthetic
-            // verification scenes — instead of the real composition host. A
-            // diagnostic for "does this machine pass the Vulkan gate, and does
-            // the backend draw?"; ignored on OpenGL.
+            // Campaign V slice V6h: run the V5/V6c bring-up harness —
+            // capability gate plus the synthetic verification scenes — instead
+            // of the real composition host. A diagnostic for "does this machine
+            // pass the Vulkan gate, and does the backend draw?". (The former
+            // ACDREAM_RENDER_BACKEND=vulkan co-requisite died with the OpenGL
+            // backend at Campaign V; this flag alone gates the harness.)
             VulkanCapabilityProbe:
                 IsExactlyOne(env("ACDREAM_VULKAN_PROBE")),
             // Campaign V slice V9: bound the probe harness to a frame budget so