feat: Wire up initiative deletion end-to-end

Add deleteInitiative tRPC procedure, wire Delete button in InitiativeCard
with confirm dialog (Shift+click bypass), remove unused onDelete prop chain.
Fix agents table FK constraints (initiative_id, account_id missing ON DELETE
SET NULL) via table recreation migration. Register conversations migration
in journal. Expand cascade delete tests to cover pages, projects, change
sets, agents (set null), and conversations (set null).

drizzle/0025_fix_agents_fk_constraints.sql

@@ -0,0 +1,32 @@
+-- Fix agents table FK constraints: initiative_id and account_id need ON DELETE SET NULL
+-- SQLite cannot ALTER column constraints, so we must recreate the table
+
+CREATE TABLE `agents_new` (
+	`id` text PRIMARY KEY NOT NULL,
+	`name` text NOT NULL,
+	`task_id` text REFERENCES `tasks`(`id`) ON DELETE SET NULL,
+	`initiative_id` text REFERENCES `initiatives`(`id`) ON DELETE SET NULL,
+	`session_id` text,
+	`worktree_id` text NOT NULL,
+	`provider` text DEFAULT 'claude' NOT NULL,
+	`account_id` text REFERENCES `accounts`(`id`) ON DELETE SET NULL,
+	`status` text DEFAULT 'idle' NOT NULL,
+	`mode` text DEFAULT 'execute' NOT NULL,
+	`pid` integer,
+	`exit_code` integer,
+	`output_file_path` text,
+	`result` text,
+	`pending_questions` text,
+	`created_at` integer NOT NULL,
+	`updated_at` integer NOT NULL,
+	`user_dismissed_at` integer
+);--> statement-breakpoint
+INSERT INTO `agents_new` SELECT
+	`id`, `name`, `task_id`, `initiative_id`, `session_id`, `worktree_id`,
+	`provider`, `account_id`, `status`, `mode`, `pid`, `exit_code`,
+	`output_file_path`, `result`, `pending_questions`,
+	`created_at`, `updated_at`, `user_dismissed_at`
+FROM `agents`;--> statement-breakpoint
+DROP TABLE `agents`;--> statement-breakpoint
+ALTER TABLE `agents_new` RENAME TO `agents`;--> statement-breakpoint
+CREATE UNIQUE INDEX `agents_name_unique` ON `agents` (`name`);

drizzle/meta/_journal.json

@@ -169,6 +169,20 @@
       "when": 1771545600000,
       "tag": "0023_rename_breakdown_decompose",
       "breakpoints": true
+    },
+    {
+      "idx": 24,
+      "version": "6",
+      "when": 1771632000000,
+      "tag": "0024_add_conversations",
+      "breakpoints": true
+    },
+    {
+      "idx": 25,
+      "version": "6",
+      "when": 1771718400000,
+      "tag": "0025_fix_agents_fk_constraints",
+      "breakpoints": true
     }
   ]
 }