feat: match fleet to blueprint targets exactly

Add an optional exact blueprint mode with keep/create/remove previews, atomic queueing, cancellation of unstarted excess creations, and persistent dependencies for safe port reuse. Track removals alongside creations and preserve fill mode as the default.

Validation: type check, production build, and 103 deployment tests passed. The full suite has one telemetry assertion failure also reproduced on the previous commit.

Fixes #42

src/routes/api/deployment-collections/preview/+server.ts

@@ -4,6 +4,6 @@ import { previewCollection } from '$lib/server/fleet/collections.js';
 export async function POST({ request }: { request: Request }) {
     try {
         const body = await request.json();
-        return json(previewCollection(body?.blueprintId));
+        return json(previewCollection(body?.blueprintId, body?.mode));
     } catch (err) { return json({ error: (err as Error).message }, { status: 400 }); }
 }