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/lib/deployment-plan.ts

@@ -32,11 +32,16 @@ export interface BlueprintSummary {
     totalServers: number;
 }
 
+export type CollectionMode = 'fill' | 'exact';
+
 export interface CollectionPreview {
     id: string;
     expiresAt: string;
     blueprintName: string;
     launchConcurrency: number;
+    mode: CollectionMode;
+    retainedServers: string[];
+    removals: { name: string; reason: string }[];
     entries: { count: number; existing: number; missing: number; existingServers: string[];
         coverage: { name: string; health: string; href: string }[]; recipe: LaunchRecipeSummary }[];
     servers: { entryIndex: number; name: string | null; port: number | null; hasSavedKey: boolean }[];
@@ -55,12 +60,14 @@ export interface CollectionSummary {
     queued: number;
     provisioning: number;
     verifying: number;
+    mode: CollectionMode;
 }
 
 export interface CollectionDetail {
     collection: CollectionSummary;
+    retainedServers: string[];
     queue: { concurrency: number; active: { id: string; server: string; state: string; stage: string }[]; queued: number };
-    servers: { id: string; server: string; port: number; map_slug: string; state: string; stage: string;
+    servers: { id: string; server: string; action: 'create' | 'destroy'; port: number | null; map_slug: string | null; state: string; stage: string;
         started_at: string; finished_at: string | null; error: string | null; server_exists: number; queuePosition: number | null }[];
 }