feat(client): atlas roads/settlements overlays + legend + server-API data delivery (T-960, T-949)

T-960: gen_l2_roads (MaintenanceAuthority-colored polylines, rail styling, junction markers) + gen_l3_settlements (size-scaled markers, capital shape, name labels) overlays — cities render on generated bodies for the first time; left-side generation legend panel (D-226 item 3, data-driven per-overlay spec, implant component library); protocol.gd decodes road_graph/settlements + the two new response types. T-949: system_index/atlas_app/overview_screen migrated off the direct star_map_data.json read to StarMapRequest over the bridge (loading state + replay-on-connect, no silent file fallback); atlas_viewer _load_markers requests CityNamesResponse for non-Sol bodies; Sol keeps the legacy authored markers.json geometry read (D-236/T-1073, load-bearing guard). Lead fix: _send_star_map_request now carries the same guard as request_star_map — the autoload's _star_map_wanted leaked across gdUnit suites and the unguarded replay-on-CONNECTED crashed 8 pre-existing flow tests on a Nil bridge; reset_test_state clears the flag. Fixtures regenerated via gen_fixtures (road/settlement samples). Full suite 2946/2946.

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

client/tests/fixtures/msgpack/atlas_response_not_found.msgpack

@@ -1 +1 @@
-ƒ§body_id¥ghost¦status¨NotFound¦layer1À
+†§body_id¥ghost¦status¨NotFound¦layer1À­district_gridÀªroad_graphÀ«settlementsÀ

client/tests/fixtures/msgpack/atlas_response_pending.msgpack

@@ -1 +1 @@
-�body_id二J1c存tatus判ending奸ayer1�
+�body_id二J1c存tatus判ending奸ayer1嶺district_grid尷road_graph屨settlements�