feat: comments marked as decisions, on top of the ticket and searchable

Whoever can change the ticket flags a comment as a decision (new event
CommentDecisionMarkedEvent on the comment). The ticket page lists its
decisions above the description, with a link to the comment in the
conversation (`?comment=<id>` scrolls to it and points at it), and the
search palette finds them by their text across my projects.

API: markDecision / PUT-DELETE /api/comments/{id}/decision; Issue.decisions
and GET /api/issues/{issue}/decisions; decisions(projectId?, search) and
GET /api/projects/{project}/decisions, GET /api/me/decisions. MCP:
mark_decision, search_decisions, and get_issue includes them.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

libs/web/tracker/application/src/lib/events/issue.events.ts

@@ -71,6 +71,7 @@ export const issuePageEvents = eventGroup({
     }>(),
     commentEditRequested: type<{ commentId: string; body: string }>(),
     reactRequested: type<{ commentId: string; emoji: string; on: boolean }>(),
+    decisionRequested: type<{ commentId: string; on: boolean }>(),
     voteRequested: type<{ issueId: string; on: boolean }>(),
     /** An image pasted into a text was uploaded (it joins the ticket's files). */
     imagePasted: type<{ issueId: string }>(),

libs/web/tracker/application/src/lib/facades/issue.facade.ts

@@ -231,6 +231,11 @@ export class IssueFacade {
     this.dispatch.reactRequested({ commentId, emoji, on });
   }
 
+  /** Marks a comment as a decision of the ticket (`on`) or unmarks it. */
+  markDecision(commentId: string, on: boolean): void {
+    this.dispatch.decisionRequested({ commentId, on });
+  }
+
   /** A copy of what the open ticket says; answers its key. */
   duplicate(): Observable<string | null> {
     const issueId = this.store.issue()?.id ?? '';

libs/web/tracker/application/src/lib/stores/issue.store.ts

@@ -423,6 +423,20 @@ export const IssueStore = signalStore(
               ),
             ),
           ),
+          events
+            .on(issuePageEvents.decisionRequested)
+            .pipe(
+              mergeMap(({ payload }) =>
+                runCommand(
+                  comments.markDecision(payload.commentId, payload.on),
+                  payload.on
+                    ? 'Marcado como decisión: sale arriba del ticket'
+                    : 'Ya no es una decisión',
+                  done,
+                  failed,
+                ),
+              ),
+            ),
           events.on(issuePageEvents.reactRequested).pipe(
             mergeMap(({ payload }) =>
               comments.react(payload.commentId, payload.emoji, payload.on).pipe(