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/domain/src/lib/ports/gateways.ts

@@ -16,6 +16,7 @@ import {
   PushDeviceSubscription,
   CommandResult,
   Comment,
+  Decision,
   Epic,
   GitIntegration,
   GitRepository,
@@ -144,6 +145,14 @@ export abstract class IssuesGateway {
   abstract pins(): Observable<IssueSummary[]>;
   /** Pins the ticket for me (or unpins it): private, at most 20. */
   abstract pin(issueId: string, pinned: boolean): Observable<void>;
+  /**
+   * Decisions (comments marked as such) of all my projects by their text,
+   * most recent first: here and not in CommentsGateway, for the palette.
+   */
+  abstract searchDecisions(
+    search: string,
+    limit: number,
+  ): Observable<Decision[]>;
   /** Tickets hanging from `issueId`. */
   abstract children(
     projectId: string,
@@ -289,6 +298,11 @@ export abstract class CommentsGateway {
     on: boolean,
   ): Observable<CommandResult>;
   abstract remove(commentId: string): Observable<CommandResult>;
+  /** Marks it as a decision of its ticket (`on`) or unmarks it. */
+  abstract markDecision(
+    commentId: string,
+    on: boolean,
+  ): Observable<CommandResult>;
 }
 
 /** A ticket's files. Uploads and downloads go through the REST API. */