feat: Add initiative review gate before push

When all phases complete, the initiative now transitions to
pending_review status instead of silently stopping. The user
reviews the full initiative diff and chooses:
- Push Branch: push cw/<name> to remote for PR workflows
- Merge & Push: merge into default branch and push

Changes:
- Schema: Add pending_review to initiative status enum
- BranchManager: Add pushBranch port + SimpleGit adapter
- Events: initiative:pending_review, initiative:review_approved
- Orchestrator: checkInitiativeCompletion + approveInitiative
- tRPC: getInitiativeReviewDiff, getInitiativeReviewCommits,
  getInitiativeCommitDiff, approveInitiativeReview
- Frontend: InitiativeReview component in ReviewTab
- Subscriptions: Add initiative events + missing preview/conversation
  event types and subscription procedures

apps/server/db/repositories/initiative-repository.ts

@@ -48,7 +48,7 @@ export interface InitiativeRepository {
    * Find all initiatives with a specific status.
    * Returns empty array if none exist.
    */
-  findByStatus(status: 'active' | 'completed' | 'archived'): Promise<Initiative[]>;
+  findByStatus(status: 'active' | 'completed' | 'archived' | 'pending_review'): Promise<Initiative[]>;
 
   /**
    * Update an initiative.

apps/server/db/schema.ts

@@ -19,7 +19,7 @@ import { relations, type InferInsertModel, type InferSelectModel } from 'drizzle
 export const initiatives = sqliteTable('initiatives', {
   id: text('id').primaryKey(),
   name: text('name').notNull(),
-  status: text('status', { enum: ['active', 'completed', 'archived'] })
+  status: text('status', { enum: ['active', 'completed', 'archived', 'pending_review'] })
     .notNull()
     .default('active'),
   mergeRequiresApproval: integer('merge_requires_approval', { mode: 'boolean' })