Consolidate documentation into architecture and merged guides

docs/getting-started.md

@@ -74,31 +74,25 @@ XDG_DATA_HOME=/tmp/gigline-campaign godot --path . --fixed-fps 60 --script res:/
 
 The unit test runner is the project's own lightweight harness (no editor plugin required) so CI can run it without the editor.
 
-## Save Data and Migration
+## Save Data
 
-The game keeps four small JSON files in Godot's `user://` directory, which is
-`~/.local/share/godot/app_userdata/Gig Line/` on Linux,
-`%APPDATA%\Godot\app_userdata\Gig Line\` on Windows and
-`~/Library/Application Support/Godot/app_userdata/Gig Line/` on macOS:
+The game writes four JSON files in Godot's `user://` directory:
 
-| File | Contents |
+| Platform | Location |
 | --- | --- |
-| `settings.json` | Camera, HUD, binding, difficulty, audio, accessibility and tutorial flags. Missing keys are filled from the current defaults; there is no schema version because the field set grew compatibly. |
-| `campaign.json` | Campaign index, completed venues, difficulty, shift number and last grade. Older files with missing fields open at the safe defaults. |
-| `shift_results.json` | Completed-shift review history, appended as an array. |
-| `shift_state.json` | Resumable mid-shift checkpoint, version `1`. It stores the venue, guard/door/flashlight/body-camera state, coordinator snapshot and NPC rows. |
+| Linux | `~/.local/share/godot/app_userdata/Gig Line/` |
+| Windows | `%APPDATA%\Godot\app_userdata\Gig Line\` |
+| macOS | `~/Library/Application Support/Godot/app_userdata/Gig Line/` |
 
-Writes go to a sibling `.tmp` file and are renamed only after the complete JSON
-is written. A corrupt or partial file is ignored on load, so the player gets
-defaults rather than a crash and a valid old file is not overwritten by a failed
-replace. The migration fixtures used by the tests live in
-`src/test/fixtures/saves/`.
+Files: `settings.json`, `campaign.json`, `shift_results.json` and the versioned
+`shift_state.json` checkpoint. The schema, migration/default-filling rules,
+atomic-write behavior and checkpoint contents are in
+[`architecture.md#persistence-and-save-contract`](architecture.md#persistence-and-save-contract).
 
 For a clean first launch, delete the four files (or the whole `Gig Line` user
 directory). Settings' **Reset campaign** clears campaign progress separately.
-To back up or move a profile, copy those files while the game is closed; to roll
-back, restore the previous copies. Shift history is diagnostic and is not
-required to resume a checkpoint.
+To back up or move a profile, copy the files while the game is closed; restore
+them to roll back. Shift history is diagnostic and not required to resume.
 
 ## Controls