fix(client): the Atlas was replaying a cache from a build that no longer existed (T-1239)

Ferrath's Global map drew no rivers at native resolution: 375 courses arrived
and 0 were drawn. The report suspected the D-261 length cull or the water
truncation. Both were innocent, and so was the renderer.

The client served the canvas from its own disk cache (T-1183). Every payload
for GJ820Bc predated T-1237 (4e503c356), which replaced one-course-per-D8-hop
with one-course-per-river -- so the map was drawing 375 hop fragments whose
longest run was 106 km, all of them under D-261's read-as-a-line floor. Same
build, same scenario, same 3440x1440, cache the only difference:

  stale   courses=375  runs=180  longest=6.0px  (~106 km)   drawn=0
  cold    courses=73   runs=23   longest=93.2px (~1,644 km) drawn=18

It looked resolution-dependent because it wasn't a resolution at all: 960x540
resolves to an 814x407 canvas, a key never cached, so it missed and re-derived
correctly. 3440x1440 resolves to 1080x540, which had an entry from 2026-08-06.
During the stale capture the server logged no course production whatsoever --
the canvas never came from it.

The cache's only invalidation signal is project.yaml's version, and 4e503c356
changed how canvases are generated without touching it, so hop-shaped entries
stayed valid. All 13 stale entries are stamped 0.4.5. 0.4.6 forces them to miss;
that, not clearing a local directory, is what repairs a player's Atlas.

The harness let this hide for eight days, in two ways now fixed. It ran against
the developer's persistent user:// cache, so a capture could render a canvas
built by a build that no longer existed -- and any golden shot in that window
silently inherited it; user:// is now isolated per run. And it sent server
stderr to /dev/null via an already-unlinked mktemp file, so no tracing from a
capture was ever reachable; the log now lives at .cache/visual-server.log.

The capture readout gained runs= and longest= between courses= and drawn=,
because "375 arrived, 0 drawn" is not one fact but three stages, and telling
them apart is what turned a guess between two suspects into a measurement.

Follow-ups filed: T-1241 (current_schema_version() returns its ?.?.? fallback in
an exported build, so a shipped game never invalidates on version at all) and
T-1242 (nothing enforces the generation-change/version-bump pairing -- this is
the fourth bump forced after the fact).

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

client/tests/visual_capture.gd

@@ -335,7 +335,7 @@ func _log_atlas_view_transform(tree_root: Node, scenario_name: String) -> void:
 		(
 			"visual_capture: view-transform[%s] rung=%s world_center=%s held_extent=%s "
 			+ "canvas_position=%s canvas_scale=%s footprint_px=%s canvas_cells=%dx%d "
-			+ "courses=%d drawn=%d settlements=%d"
+			+ "courses=%d runs=%d longest=%.1fpx drawn=%d settlements=%d"
 		)
 		% [
 			scenario_name,
@@ -348,6 +348,8 @@ func _log_atlas_view_transform(tree_root: Node, scenario_name: String) -> void:
 			int(summary.get("canvas_width", 0)),
 			int(summary.get("canvas_height", 0)),
 			int(summary.get("course_count", 0)),
+			int(summary.get("runs_built", 0)),
+			float(summary.get("longest_run_px", 0.0)),
 			int(summary.get("drawn_course_count", 0)),
 			int(summary.get("settlement_count", 0)),
 		]

client/ui/implant/apps/atlas/step_canvas/step_canvas_annotation_layer.gd

@@ -206,6 +206,16 @@ var _body_radius_km: float = 0.0
 ## (D-261). Entries: {points: PackedVector2Array, terminus: String, taper: bool}.
 var _prepared_courses: Array = []
 
+## Preparation stage counts, for telling apart the three ways a river can fail
+## to appear (T-1239). "375 courses arrived and 0 were drawn" is not one fact
+## but a chain: courses arrive, the water clip splits them into runs, the length
+## cull drops the short runs. Without the intermediate counts every failure
+## looks identical from a capture, which is how T-1239 sat as "suspect the cull
+## OR the water truncation" instead of a measurement. Cheap: three integers
+## written once per canvas adoption, never per frame.
+var _runs_built: int = 0
+var _longest_run_px: float = 0.0
+
 
 ## Adopt a new canvas + its request frame (world center, rung, extent, body
 ## radius) — the world->screen projection for every drawn feature depends on
@@ -249,6 +259,8 @@ func clear_frame() -> void:
 ## dropped entirely rather than drawn as specks.
 func _prepare_courses() -> void:
 	_prepared_courses.clear()
+	_runs_built = 0
+	_longest_run_px = 0.0
 	if not _canvas is Dictionary:
 		return
 	var d: Dictionary = _canvas
@@ -298,6 +310,8 @@ func _flush_run(
 ) -> void:
 	if run.size() < 2:
 		return
+	_runs_built += 1
+	_longest_run_px = maxf(_longest_run_px, _polyline_length_px(run))
 	_prepared_courses.append(
 		{
 			"points": run,
@@ -351,6 +365,21 @@ func get_drawn_course_count() -> int:
 	return _prepared_courses.size()
 
 
+## Runs the water clip produced, before the length cull (T-1239 diagnostic).
+## Read with get_drawn_course_count(): runs_built == 0 means the water clip ate
+## everything; runs_built high with drawn 0 means the cull did.
+func get_runs_built() -> int:
+	return _runs_built
+
+
+## The longest run's on-screen length in px, before the cull (T-1239). Compared
+## against MIN_COURSE_LENGTH_PX it says whether the threshold was near-miss or
+## nowhere close — the difference between "tune the constant" and "the geometry
+## is wrong".
+func get_longest_run_px() -> float:
+	return _longest_run_px
+
+
 static func _polyline_length_px(pts: PackedVector2Array) -> float:
 	var total: float = 0.0
 	for i in range(1, pts.size()):

client/ui/implant/apps/atlas/step_canvas/step_canvas_viewer.gd

@@ -434,6 +434,10 @@ func get_current_canvas_summary() -> Dictionary:
 		"drawn_course_count": (
 			_annotation_layer.get_drawn_course_count() if _annotation_layer else 0
 		),
+		# T-1239: the two stages between "arrived" and "drawn", so a capture can
+		# say WHICH stage dropped the rivers instead of only that they are gone.
+		"runs_built": _annotation_layer.get_runs_built() if _annotation_layer else 0,
+		"longest_run_px": _annotation_layer.get_longest_run_px() if _annotation_layer else 0.0,
 		"course_count_by_class": course_count_by_class,
 		"cliff_count": (d.get("cliffs", []) as Array).size(),
 		"settlement_count": _count_distinct_settlements(d),