Snapshot URL datasets locally on add; preview tabular data as a table

docs/architecture/02-persistence.md

@@ -6,19 +6,20 @@ How Astrolabe stores data in the browser, and the rules that keep that storage t
 
 ## 1. The Infrastructure-Adapter Principle
 
-**Rule: nothing outside `src/app/infrastructure/` ever touches `indexedDB`, `localStorage`, `window`, or `location` directly.** Every browser-storage interaction goes through a typed adapter module that exposes plain async functions returning domain objects.
+**Rule: nothing outside `src/app/infrastructure/` ever touches `indexedDB`, `localStorage`, `window`, `location`, or `fetch` directly.** Every browser interaction (storage _and_ network) goes through a typed adapter module that exposes plain async functions returning domain objects.
 
 ```
 src/
 ├── core/                    # portable engine — NO browser APIs, NO React
 ├── app/
-│   ├── stores/              # Zustand stores; calls infrastructure, never IDB
-│   ├── services/            # business logic; calls infrastructure, never IDB
-│   └── infrastructure/      # the ONLY place that imports indexedDB/localStorage
+│   ├── stores/              # Zustand stores; calls infrastructure, never IDB/fetch
+│   ├── services/            # business logic; calls infrastructure, never IDB/fetch
+│   └── infrastructure/      # the ONLY place that imports indexedDB/localStorage/fetch
 │       ├── snippet-store.ts     # IndexedDB: snippets (metadata + drafts)
 │       ├── dataset-store.ts     # IndexedDB: datasets (heavy payloads)
 │       ├── settings-store.ts    # localStorage: UserSettings
-│       └── ux-prefs.ts          # localStorage: app/UI prefs (sort, panel layout)
+│       ├── ux-prefs.ts          # localStorage: app/UI prefs (sort, panel layout)
+│       └── remote-data.ts       # network: fetch a URL dataset's body (the ONLY fetch)
 ```
 
 ### Why this boundary exists
@@ -29,7 +30,15 @@ src/
 - **Failure containment.** Quota errors, corrupt JSON, and missing keys are handled at the boundary and converted into typed results (or sane fallbacks), so the rest of the app never sees a raw `DOMException`.
 
 > **Do:** `import { saveSnippet } from '@/app/infrastructure/snippet-store'`
-> **Don't:** `indexedDB.open(...)` or `localStorage.getItem(...)` anywhere in a component, store, or service.
+> **Don't:** `indexedDB.open(...)`, `localStorage.getItem(...)`, or `fetch(...)` anywhere in a component, store, or service.
+
+### Background vs. interactive adapters
+
+Most adapters are driven by **background subscribers** (arch 01 §5, _Effects_): a store changes, a startup subscriber writes it through to IndexedDB — the store never calls the adapter itself. The **network** adapter is the exception. Fetching a URL dataset is a user-initiated action with its own pending/error UI, so the **component** calls `remote-data.ts` directly (components may call adapters — cf. `navigator.clipboard`) and hands the fetched body to **pure** store actions (`DatasetStore.commitUrlSnapshot` / `refreshDataset`). The store never fetches, so it stays browser-free and unit-testable on already-fetched text.
+
+> **Rule:** keep `fetch` behind `remote-data.ts`; orchestrate the URL-dataset fetch in the _component_ (busy state + the "paste data inline instead" recovery), not the store. Store commit actions only ever receive already-fetched text.
+
+**URL-dataset snapshot lifecycle** (the files a change to it touches): add / Refresh → component fetches (`infrastructure/remote-data.ts`) → `core/dataset.snapshotFromText` shapes the body by sniffed format → `DatasetStore.commitUrlSnapshot` / `refreshDataset` snapshots + profiles it _exactly like inline data_ → render resolves it cached-first in `core/rendering.resolvedData` (a live-URL fallback applies only while a URL dataset is still unfetched). See spec §05 for the behavior.
 
 ---
 
@@ -221,6 +230,8 @@ export async function saveSnippet(s: Snippet): Promise<void> {
 > **Do:** default `version` to the earliest shape (`1`) when the field is absent.
 > **Don't:** branch on the presence of individual fields scattered through the app to detect "old data." Centralize that knowledge in the migration function.
 
+> **Mirror shape changes in the import normalizer.** Imported records are built from a file, not read from IndexedDB, so they **never pass through `migrate<Entity>`** — `core/import-normalize.ts` upgrades them independently. A migration that changes a field's _shape_ must be applied in both places or import produces a malformed record. (E.g. the dataset v1→v2 URL-snapshot reshaping — address moves from `data` into `url`, `data` cleared — lives in **both** `migrateDataset` and `normalizeDataset`.)
+
 ---
 
 ## 5. localStorage Preferences (Settings & App/UI Prefs)