Add smoke_test_enter_world.gd + doc update that never made it into PR #50

Both were verified (9/9 passing) before PR #50 merged but got lost in the
handoff between my push and the concurrent live agent session reusing the
same workspace -- PR #50's actual merged diff only had the world_list.gd/
player.gd code changes, missing the new test file and the doc update.
Caught while auditing everything feeding PC2 for real completeness.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01M6rUEynmv2QmweocAQYARN

docs/testing/test_inventory.md

@@ -7,14 +7,14 @@ to know what "run the tests" actually checked.
 
 Run everything below in one shot with `scripts/run_checkpoint_tests.py`.
 
-Last verified against `main`: 2026-08-20 — full PC1 checkpoint run,
-migrations + pytest + all 7 Godot smoke tests + both platform exports, all
-clean. Real bugs found and fixed via real playtesting this same day (not
-caught by the checkpoint suite as it stood before today): the main menu
-had no way to actually open the login/register form, the world list's
-cards rendered at ~1px wide once real data existed, and navigating Play →
-Back logged the user out despite a still-valid session. All three are now
-covered by the smoke tests below so they can't silently regress.
+Last verified against `main`: 2026-08-21 — migrations + pytest + all 10
+Godot smoke tests, all clean. PC1's real playtest-found bugs (login form
+unreachable, 1px world cards, Play → Back losing the session) are covered
+by the smoke tests below so they can't silently regress. PC2 (basic
+playable world + character + movement) landed 2026-08-20/21 — see
+`docs/checkpoints/` once a PC2 record exists, and the three new smoke
+tests below (`smoke_test_test_level.gd`, `smoke_test_player.gd`,
+`smoke_test_enter_world.gd`) for what's actually verified.
 
 ## Backend — `backend/tests/` (pytest)
 
@@ -53,7 +53,7 @@ these yet):
 
 ## Godot client — `scripts/smoke_test_*.gd`
 
-**7 smoke tests merged into `main`.** Each needs a live backend —
+**10 smoke tests merged into `main`.** Each needs a live backend —
 `AGP_API_BASE_URL` env var, falling back to the
 `application/agp/api_base_url` project setting (default
 `http://127.0.0.1:8000`) if unset.
@@ -67,6 +67,9 @@ these yet):
 | `smoke_test_main_menu_ui.gd` | Instantiates `main_menu.tscn`, confirms the auth panel starts hidden, and confirms a **real signal emission** on LoginButton/RegisterButton (not calling the handler method directly) actually opens it. This is the check that would have caught 2026-08-20's real bug: the auth panel and its logic were fully correct, but nothing in the scene was ever wired to open it, so Login/Register were completely unreachable from the UI. |
 | `smoke_test_main_menu_full_flow.gd` | Full click-through: open the register form, fill it exactly as a user would, submit, confirm Play actually becomes enabled, the welcome message shows, and the auth buttons hide themselves. Calls the submit handler directly (awaited) rather than via `auth_button.pressed.emit()` — see the note at the top of the file: a synthetic `.emit()` on an `await`-using handler doesn't get driven forward reliably in `--script`/SceneTree headless mode the way real GUI input event dispatch does, confirmed by comparing direct-call vs `.emit()` behavior. Not a bug in the actual click-driven flow, just a headless-test-harness quirk to route around when writing tests. |
 | `smoke_test_main_menu_back.gd` | Regression test for Play → Back logging the user out even with a valid token still held. Registers a user, loads `main_menu.tscn` (asserts it restores the authenticated state via a real `auth_state_ready` signal wait, not a frame-count guess), clicks Play → `world_list.tscn`, clicks Back → `main_menu.tscn`, and asserts the menu is still authenticated. Checks `WelcomeLabel.is_visible_in_tree()`, not just `.visible` — the label lives inside AuthPanel, so `.visible` alone is a false positive if the panel itself is hidden (a real bug briefly present: `_show_authenticated()` hid AuthPanel while claiming the welcome label was visible, which rendered nothing). |
+| `smoke_test_test_level.gd` | Loads `scenes/worlds/test_level.tscn` directly (the level is player-agnostic and self-contained per `docs/architecture/pc2_test_level.md` §4) and confirms it has real content: 5 props, a `DirectionalLight3D` ("Sun"), and a `WorldEnvironment` — not an empty void. |
+| `smoke_test_player.gd` | Loads `scenes/game.tscn` and confirms the player exists as a real `CharacterBody3D` with a `CollisionShape3D`+shape, a `CapsuleMesh`, and spawns at the level's `PlayerSpawn` marker position. Also asserts `JUMP_VELOCITY` is positive and a `Camera3D` exists and is `current` — both were real bugs found 2026-08-20/21 (jump velocity was negative, pushing the player down instead of up; no camera existed at all, so the game was unplayable even though the character could technically move). Structural checks only — real movement/jump *direction* correctness was verified separately via a throwaway headless physics simulation during development, not by an automated test that's part of this suite. |
+| `smoke_test_enter_world.gd` | The full PC2 path end to end: register → seed a real world → load `world_list.tscn` → click the real "Enter World" button on a real card (found by walking the card's children, not by index, so it doesn't silently pass if the card layout changes) → confirms `scenes/game.tscn` actually becomes `current_scene` with the player spawned at the level's `PlayerSpawn` marker → sends a real `KEY_ESCAPE` input event (not a direct method call) and confirms it returns to `world_list.tscn`. This is the test that proves "browse → enter → walk around → leave" actually works as one continuous flow, not just that each piece works in isolation. |
 
 Run (once, to build the class cache): `godot --headless --path . --import`,
 then for each smoke test: `godot --headless --path . --script