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>

apps/ssp/src/app/brief/application/brief.store.spec.ts

@@ -179,7 +179,7 @@ const filledView: BriefView = { ...view, brief: filledBrief };
 
 function loadedBrief(store: BriefStore): Brief {
   const s = store.model();
-  if (s.tag !== 'loaded') throw new Error('not loaded');
+  if (s.tag !== 'Loaded') throw new Error('not loaded');
   return s.brief;
 }
 
@@ -431,7 +431,7 @@ describe('BriefStore.load — 404 tolerance (RB-22)', () => {
 
     // Then reset() ran exactly once, and the store ends up loaded from its result.
     expect(reset).toHaveBeenCalledTimes(1);
-    expect(store.model().tag).toBe('loaded');
+    expect(store.model().tag).toBe('Loaded');
   });
 
   it('a second 404 does not drive a second reset()', async () => {
@@ -447,6 +447,6 @@ describe('BriefStore.load — 404 tolerance (RB-22)', () => {
     // Then reset() ran exactly once — the once-only bound holds across calls, not
     // just within one — and the second 404 surfaces as an ordinary load failure.
     expect(reset).toHaveBeenCalledTimes(1);
-    expect(store.model()).toEqual({ tag: 'failed', reason: BRIEF_LOAD_FAILED });
+    expect(store.model()).toEqual({ tag: 'Failed', reason: BRIEF_LOAD_FAILED });
   });
 });