refactor: fold machine-remote-data into remote-data.ts, PascalCase load lifecycle (RD-11)

`machine-remote-data.ts` defined a third encoding of an in-flight fetch:
`LoadLifecycle`. It had three call sites, all one identical line, and the type
was never imported by name. Move the mapping into `remote-data.ts` as
`fromLoadLifecycle`, beside its neighbour `fromResource` — a `RemoteData`
constructor, not a sixth encoding.

The lowercase `loading`/`failed`/`loaded` tags on `BriefState`,
`OrgTemplateState` and `StamdataEditorState` existed only because
`LoadLifecycle` required them. Now that the constraint is inline and
PascalCase, the three machines' load-lifecycle tags become `Loading`,
`Failed` and `Loaded` — matching their own PascalCase message tags in the
same file. `stamdata-editor.machine.spec.ts` no longer asserts a PascalCase
message producing a lowercase state.

`BriefStatus` (the letter's draft/submitted/approved/rejected/sent status,
parsed off the wire from `BriefViewDto`) is a separate tag family and is
untouched — its tag count stays 54 before and after this change.

Delete `machine-remote-data.ts` and merge its spec into `remote-data.spec.ts`.
Regenerate `behaviour-spec.mdx` (the `machineRemoteData` section heading
becomes `fromLoadLifecycle`) and confirm `gen:snippets` reports no drift, since
`remote-data.ts` carries a showcase region.

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

libs/shared/src/application/remote-data.spec.ts

@@ -1,5 +1,5 @@
 import { describe, it, expect } from 'vitest';
-import { RemoteData, map2, map, successOf } from './remote-data';
+import { RemoteData, fromLoadLifecycle, map2, map, successOf } from './remote-data';
 import { loading, failure, empty, success } from '../testing/remote-data';
 
 const loadingRd: RemoteData<string, number> = loading();
@@ -33,3 +33,20 @@ describe('successOf', () => {
     expect(successOf(empty())).toBeUndefined();
   });
 });
+
+describe('fromLoadLifecycle', () => {
+  it('maps Loading → Loading', () => {
+    expect(fromLoadLifecycle({ tag: 'Loading' })).toEqual(loading());
+  });
+
+  it('maps Failed → Failure carrying an Error with the reason', () => {
+    const rd = fromLoadLifecycle({ tag: 'Failed', reason: 'boom' });
+    expect(rd.tag).toBe('Failure');
+    if (rd.tag === 'Failure') expect(rd.error.message).toBe('boom');
+  });
+
+  it('maps Loaded → Success carrying the whole loaded state', () => {
+    const loadedState = { tag: 'Loaded', foo: 42 } as const;
+    expect(fromLoadLifecycle(loadedState)).toEqual(success(loadedState));
+  });
+});