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

src/language/diagnostics.ts

@@ -3,6 +3,7 @@ import * as vscode from 'vscode';
 import { ArchifyDiagnostic, isEvidenceError, validate } from '../archify/cli';
 import { evidenceMode, runtimeFor } from '../archify/runtime';
 import { ModelProblem, isRegistryFile, parseRegistry } from '../model/format';
+import { isDecisionFile, parseDecision } from '../model/decisions';
 import { prepareDiagram } from '../model/prepare';
 import { ModelService } from '../model/service';
 import { isArchifyFile } from '../sources/detect';
@@ -70,7 +71,7 @@ export class DiagnosticsController implements vscode.Disposable {
   }
 
   private schedule(doc: vscode.TextDocument, delay: number): void {
-    if (!JSON_LANGUAGES.has(doc.languageId) && !isArchifyFile(doc.fileName) && !isRegistryFile(doc.fileName)) return;
+    if (!JSON_LANGUAGES.has(doc.languageId) && !isArchifyFile(doc.fileName) && !isRegistryFile(doc.fileName) && !isDecisionFile(doc.fileName)) return;
     const key = doc.uri.toString();
     clearTimeout(this.timers.get(key));
     this.timers.set(key, setTimeout(() => void this.validate(doc), delay));
@@ -91,6 +92,10 @@ export class DiagnosticsController implements vscode.Disposable {
       await this.validateRegistry(doc, seq);
       return;
     }
+    if (isDecisionFile(doc.fileName)) {
+      await this.validateDecision(doc, seq);
+      return;
+    }
     if (isArchifyFile(doc.fileName)) {
       // Nothing else reports YAML syntax errors in .archify files, and a file
       // that does not parse has no diagram to validate yet.
@@ -179,6 +184,27 @@ export class DiagnosticsController implements vscode.Disposable {
   }
 
   /** A registry file: its own YAML and element problems, plus duplicates across the model. */
+  private async validateDecision(doc: vscode.TextDocument, seq: number): Promise<void> {
+    const text = doc.getText();
+    const root = await this.models.rootOf(doc.uri);
+    const rel = root ? path.relative(root.fsPath, doc.uri.fsPath).split(path.sep).join('/') : path.basename(doc.uri.fsPath);
+    const problems: ModelProblem[] = [...parseDecision(text, rel).problems];
+    if (root) {
+      try {
+        const index = await this.models.index(root);
+        for (const problem of index.decisions.problems) {
+          if (problem.file === rel && !problems.some((p) => p.message === problem.message)) problems.push(problem);
+        }
+      } catch {
+        // The index reports its own failures when the model page opens.
+      }
+    } else {
+      problems.push({ message: `This decision has lost its model: no main.archify above ${path.basename(doc.uri.fsPath)}, so its elements and diagrams cannot be resolved.`, severity: 'warning', line: 0 });
+    }
+    if (seq !== this.sequence.get(doc.uri.toString()) || doc.isClosed) return;
+    this.collection.set(doc.uri, problems.map((problem) => this.modelDiagnostic(doc, text, 'yaml', problem)));
+  }
+
   private async validateRegistry(doc: vscode.TextDocument, seq: number): Promise<void> {
     const text = doc.getText();
     const root = await this.models.rootOf(doc.uri);