feat(rules): project rule + topic suppressions

Lets a project mute individual rules or whole topics from rulebooks it
subscribes to, without unsubscribing the rulebook. Two new association
tables (migration 0060), 4 MCP tools (suppress/unsuppress × rule/topic),
4 REST endpoints, and an inline "× skip" affordance plus collapsed
"Suppressed (N)" section in the project's Rules tab.

get_applicable_rules now emits suppressed_rules and suppressed_topics
(detail objects with rulebook/topic context, not just IDs) so the UI
can render the suppressed list without a follow-up lookup. The main
rules projection grew topic_id and rulebook_id columns for the per-row
suppress affordance.

Project deletion cascades the suppression rows via hard DELETE — they
are pure associations with no soft-delete column, and restoring a
deleted project should start fresh, not inherit stale mutes.

Project-scoped rules (Rule.project_id) are deliberately not suppressible
— delete them with delete_rule instead.

Implements plan-task #187.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

frontend/src/api/rulebooks.ts

@@ -45,7 +45,9 @@ export interface ApplicableRules {
     id: number;
     title: string;
     statement: string;
+    topic_id: number;
     topic_title: string;
+    rulebook_id: number;
     rulebook_title: string;
   }[];
   project_rules: {
@@ -53,6 +55,20 @@ export interface ApplicableRules {
     title: string;
     statement: string;
   }[];
+  suppressed_rules: {
+    id: number;
+    title: string;
+    topic_id: number;
+    topic_title: string;
+    rulebook_id: number;
+    rulebook_title: string;
+  }[];
+  suppressed_topics: {
+    id: number;
+    title: string;
+    rulebook_id: number;
+    rulebook_title: string;
+  }[];
   truncated: boolean;
   subscribed_rulebooks: { id: number; title: string }[];
 }
@@ -147,3 +163,21 @@ export async function createProjectRule(
 ): Promise<Rule> {
   return apiPost(`/api/projects/${projectId}/rules`, data);
 }
+
+// ── Suppressions ───────────────────────────────────────────────────
+
+export async function suppressRuleForProject(projectId: number, ruleId: number): Promise<void> {
+  await apiPost(`/api/projects/${projectId}/suppressions/rules/${ruleId}`, {});
+}
+
+export async function unsuppressRuleForProject(projectId: number, ruleId: number): Promise<void> {
+  return apiDelete(`/api/projects/${projectId}/suppressions/rules/${ruleId}`);
+}
+
+export async function suppressTopicForProject(projectId: number, topicId: number): Promise<void> {
+  await apiPost(`/api/projects/${projectId}/suppressions/topics/${topicId}`, {});
+}
+
+export async function unsuppressTopicForProject(projectId: number, topicId: number): Promise<void> {
+  return apiDelete(`/api/projects/${projectId}/suppressions/topics/${topicId}`);
+}