fix(simulation): PR #191 review round — n-clamp mirror, min_wl band quantization, coalescing coverage, fixture consumer

All seven Hoshe/Tyre findings addressed, none retracted:
- n-clamp/echo/staleness triangle (Tyre C1): client _clamp_window_n_mirror
  (bit-for-bit twin of the server clamp, canonicalize_district_center
  precedent) applied before _n is stored/sent; server test pins the
  quarter n=32 -> echo 16 contract.
- min_wl band quantization (Hoshe 1/Tyre C3): quantize_min_wl_m snaps to
  MIN_WL_BANDS_M {0, 32768, 16384, 8192, 4096} before cache key and echo
  (design doc §5's unbounded-key fix), reusing the one true
  OCTAVE_WAVELENGTHS_M array; docstrings now state the server-quantizes/
  client-sends-raw split; same-band cache-sharing test.
- coalescing granularity axis (Hoshe 2): two tests pin different-
  granularity requests as separate in-flight slots and same-granularity
  coalescing unchanged.
- orphaned fixture (Hoshe 3): test_protocol.gd consumer decodes
  atlas_response_ready_with_window.msgpack through the real IPC path and
  asserts the new fields.
- atlas_window_request coverage (Hoshe 4): new test file — stale-drop on
  granularity mismatch, old-server-shape defaults accepted, clamp mirror
  formula + wiring. First draft's quarter-via-request_now test would have
  passed for the wrong reason (request_now resets granularity by design
  until T-1153) — split into formula pin + reachable-path wiring proof.
- granularity type seam (Tyre C2): field + resolver docstrings state
  finer-only integer multiples with resolve_window_granularity as the
  single widening point; matching contract note added to the D-226
  T-1143-rulings amendment.

cargo --lib 1807/1807; goldens bit-identical; gdlint clean.

client/tests/test_protocol.gd

@@ -511,6 +511,27 @@ func test_decode_atlas_response_not_found() -> void:
 	assert_that(resp.status).is_equal("NotFound")
 
 
+## PR #191 review, Hoshe 3: `atlas_response_ready_with_window.msgpack` had NO
+## consumer anywhere in client/tests — regenerated by the T-1150 `granularity`/
+## `min_wl_m` field additions but nothing decoded it through the real IPC path.
+## This is that consumer, matching the sibling `test_decode_atlas_response_*`
+## tests' style/fixture-dir convention above: full decode_atlas_layer_response()
+## round trip (not a hand-built Dictionary like test_atlas_data_delivery.gd's
+## passthrough tests), confirming `district_window.granularity`/`.min_wl_m`
+## (T-1150's two new echo fields) survive the real client decode path.
+func test_decode_atlas_response_ready_with_window() -> void:
+	var bytes := _load_fixture("atlas_response_ready_with_window")
+	var resp = Protocol.decode_atlas_layer_response(bytes)
+	assert_that(resp).is_not_null()
+	assert_that(resp.status).is_equal("Ready")
+	assert_that(resp.district_window).is_not_null()
+	var window: Dictionary = resp.district_window
+	assert_that(window.get("center")).is_equal([10, -5])
+	assert_that(int(window.get("n"))).is_equal(2)
+	assert_that(int(window.get("granularity"))).is_equal(1)
+	assert_that(int(window.get("min_wl_m"))).is_equal(0)
+
+
 func test_snapshot_is_not_decoded_as_atlas_response() -> void:
 	# Disambiguation: an ObserverSnapshot has no "status" key, so the atlas
 	# decoder rejects it. receive_bytes relies on this to route correctly.