step 3: add widget shell sizing and frame pump

AGENTS.md

@@ -2,16 +2,17 @@
 
 ## Current status
 
-Step 2 complete.
+Step 3 complete.
 
 ## Completed steps
 
 Step 1 - Public API contract and pure core.
 Step 2 - Thread-safe state, commands, overlays, and cache model.
+Step 3 - Widget shell, sizing system, and GUI-thread frame pump.
 
 ## Current step
 
-Step 3 - Widget shell, sizing system, and GUI-thread frame pump.
+Step 4 - Tile manager, persistent cache, and asynchronous loading.
 
 ## Design decisions
 
@@ -40,6 +41,13 @@ None yet.
 - Implemented public runtime overlay/view/layer/provider/cache/debug wrappers against logical state without Dear PyGui calls.
 - Implemented memory cache metadata, disk cache path generation, metadata read/write, disk size scanning, and prune planning.
 - Added Step 2 tests for command coalescing, overlay/view isolation, copied trajectory inputs, coordinate length validation, layer state, disk path generation, and prune ordering.
+- Implemented `map_widget(...)` as a Dear PyGui child-window plus drawlist shell.
+- Implemented GUI-thread renderer frame pump that schedules frame callbacks, drains command queues, measures size, resizes the drawlist, and draws a placeholder background/attribution.
+- Implemented sizing helpers for measured size, last non-zero size preservation, visibility transitions, effective draw size, and resize dirty flags.
+- Implemented map interaction hit-rectangle calculation.
+- Added Step 3 examples for basic map, window sizing, child-window sizing, table sizing, and hidden-tab sizing.
+- Added Step 3 tests for sizing transitions, zero-size preservation, resize dirty flags, command drain ordering, and hit rectangles.
+- Ran a Dear PyGui context smoke check for `map_widget` child-window/drawlist creation.
 - Ran `uv run pytest`.
 - Ran `uv run ruff check .`.
 - Ran `uv run ruff format .`.
@@ -48,4 +56,4 @@ None yet.
 
 ## Next action
 
-Implement Step 3.
+Implement Step 4.