feat(client): T-1153 + T-1152 client half — continuous cursor-anchored zoom ladder, Region-rung orbital entry, click-through retired

The atlas 'regional' screen now opens the LADDER at the canonical orbital
frame (Region granularity, whole body fitted and centered) and wheel zoom
descends continuously — cursor-anchored, unclamped across rungs, with
progressive refinement (held composite keeps drawing, finer rung swaps in
place on arrival; no blank frame, no mode flip). Full-zoom-out resets to
the canonical planetary frame per Jeroen's HARD condition
(is_fully_zoomed_out = extent >= body circumference, not a zoom-value
heuristic). The district_screen nav hop is deleted — D-013 restored:
descent is a zoom gesture, not a nav push. AtlasViewer's heightmap-texture
path is unreachable from nav (code intact; overlay surface deferred, see
report/tickets).

Rung selection: design doc §5's literal formula has NO legal District band
at any real viewport (visual-tolerance band and n=64 coverage ceiling
never overlap — pinned by executable boundary tests at 1600x900);
select_rung() splits it into a coverage ceiling (decides Region) then the
2x visual tolerance (District vs Quarter), documented at the function.
In practice the ladder steps Region -> Quarter directly.

Wire: window_granularity_v2 encoded (omitted at District for byte-compat),
granularity_v2 echoed value keyed + staleness-guarded end to end; Region
clamp mirror replicates the server's bounded halving loop (no closed
form). MIN/MAX_ZOOM widened to [0.0005, 64] — the old 0.5 floor would
have clamped a real body's canonical fit zoom, violating the reset
condition.

Real pre-existing bug fixed in atlas_window_overlay.gd: the draw path used
echoed n as both cell-grid dimension and district extent — only
coincidentally correct at District granularity; Quarter/Region would have
read wrong array offsets. cell_grid_side_for_window() now mirrors the
server's WindowGranularity::cell_grid_side.

Tests: +26 pure-function geometry tests, new 30-test zoom-ladder suite,
extensions across the window cache/request/overlay/delivery suites.
Full suite 3518 green; cold-parse clean.

client/scripts/autoloads/sim_bridge.gd

@@ -435,20 +435,32 @@ func send_named_action(action_name: String, action_data: Variant = null) -> void
 ##
 ## window_granularity/window_min_wl_m (T-1150): struct/key plumbing for the
 ## zoom-ladder quarter rung — district (0/omitted) stays the default for
-## every caller in this codebase today; requesting quarter granularity is
-## T-1153's job, not wired here.
+## every caller in this codebase today.
+##
+## window_granularity_v2 (T-1152/T-1153): the R5-redesigned string-tag
+## granularity ("Quarter"/"District"/"Region") — the ONLY way to request the
+## coarser-than-district Region rung the legacy u32 field cannot express.
+## Empty string (omitted) is the default for every caller that doesn't pass
+## it, byte-compatible with every pre-T-1152 request.
 func request_atlas_layers(
 	body_id: String,
 	up_to: String = "Topography",
 	window_center: Variant = null,
 	window_n: int = 0,
 	window_granularity: int = 0,
-	window_min_wl_m: int = 0
+	window_min_wl_m: int = 0,
+	window_granularity_v2: String = ""
 ) -> void:
 	if test_mode or _bridge == null or state != ConnectionState.CONNECTED:
 		return
 	var bytes := Protocol.encode_atlas_layer_request(
-		body_id, up_to, window_center, window_n, window_granularity, window_min_wl_m
+		body_id,
+		up_to,
+		window_center,
+		window_n,
+		window_granularity,
+		window_min_wl_m,
+		window_granularity_v2
 	)
 	if bytes.is_empty():
 		return