Architecture decisions: files, diagram references, views and panels

- *.archify-decision files: id (unique, words), title, status, date,
  elements, diagrams, supersedes, and prose; parsed, merged and link-checked
  in the model index; diagnostics on the file
- diagrams point at decisions with decisions: [...] on the diagram, nodes
  and edges; stripped before Archify, unknown ids reported, completion,
  hover and go-to-definition for the ids and for elements/diagrams/
  supersedes in decision files
- Decisions panel on the main.archify page; Decisions rail panel under a
  diagram (hover lights up the node or connection); decisions on element
  cards and in the element dialog; decision view for the file, with a
  lost-model note outside a model
- Archify | New Decision… command and template; editor schemas; the three
  New Model examples carry decisions; docs, changelog, 0.8.0

test/integration/suite.ts

@@ -329,6 +329,26 @@ export async function run(): Promise<void> {
     assert.equal(editor.document.languageId, 'yaml');
   });
 
+  await check('a .archify-decision file opens as the decision view; an unknown decision id is a problem in a diagram', async () => {
+    const decision = workspaceFile('model/decisions/0002-queue-between-api-and-worker.archify-decision');
+    await vscode.commands.executeCommand('vscode.open', decision);
+    const tab = await waitFor('decision view tab', () =>
+      vscode.window.tabGroups.all.flatMap((g) => g.tabs).find((t) => t.isActive && t.input instanceof vscode.TabInputCustom && t.input.viewType === 'archify.decision' && t.input.uri.toString() === decision.toString()),
+    );
+    assert.ok(tab);
+    // A diagram that points at a decision nobody defines.
+    const bad = workspaceFile('model/0300-components/bad-decision.archify');
+    await vscode.workspace.fs.writeFile(bad, Buffer.from('schema_version: 1\ndiagram_type: architecture\nmeta:\n  title: Bad\n  output: bad.html\ndecisions: [nobody-decided]\ncomponents:\n  - ref: api\n    pos: [40, 60]\n    size: [130, 60]\n    decisions: [queue-between-api-and-worker]\n', 'utf8'));
+    const doc = await vscode.workspace.openTextDocument(bad);
+    await vscode.window.showTextDocument(doc);
+    const problem = await waitFor('unknown decision problem', () =>
+      vscode.languages.getDiagnostics(doc.uri).find((d) => d.source === 'archify' && /Unknown decision "nobody-decided"/.test(d.message)),
+    );
+    assert.equal(problem.range.start.line, 5);
+    assert.ok(!vscode.languages.getDiagnostics(doc.uri).some((d) => /queue-between-api-and-worker/.test(d.message)), 'the known decision is not reported');
+    await vscode.workspace.fs.delete(bad);
+  });
+
   await check('Archify | New Diagram… → Model creates main.archify from the folder name', async () => {
     const folder = workspaceFile('new-shop');
     await vscode.workspace.fs.createDirectory(folder);
@@ -385,7 +405,7 @@ export async function run(): Promise<void> {
     assert.match(content, /name: Shop two/);
     assert.match(content, /title: Shop two — overview/);
     const names = (await vscode.workspace.fs.readDirectory(folder)).map(([name]) => name).sort();
-    assert.deepEqual(names, ['0100-context', '0200-containers', '0300-components', 'main.archify', 'registry']);
+    assert.deepEqual(names, ['0100-context', '0200-containers', '0300-components', 'decisions', 'main.archify', 'registry']);
     const registry = (await vscode.workspace.fs.readDirectory(vscode.Uri.joinPath(folder, 'registry'))).map(([name]) => name).sort();
     assert.deepEqual(registry, ['containers.archify-registry', 'people.archify-registry', 'systems.archify-registry']);
     const tab = await waitFor('model page tab', () =>