feat: add prompt resources, fix MCP proxy transport, enrich tool descriptions

- Fix MCP proxy to support SSE and STDIO transports (not just HTTP POST)
- Enrich tool descriptions with server context for LLM clarity
- Add Prompt and PromptRequest resources with two-resource RBAC model
- Add propose_prompt MCP tool for LLM to create pending prompt requests
- Add prompt resources visible in MCP resources/list (approved + session's pending)
- Add project-level prompt/instructions in MCP initialize response
- Add ServiceAccount subject type for RBAC (SA identity from X-Service-Account header)
- Add CLI commands: create prompt, get prompts/promptrequests, approve promptrequest
- Add prompts to apply config schema
- 956 tests passing across all packages

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/db/prisma/schema.prisma

@@ -170,6 +170,7 @@ model Project {
   id          String   @id @default(cuid())
   name        String   @unique
   description String   @default("")
+  prompt      String   @default("")
   proxyMode   String   @default("direct")
   llmProvider String?
   llmModel    String?
@@ -178,8 +179,10 @@ model Project {
   createdAt   DateTime @default(now())
   updatedAt   DateTime @updatedAt
 
-  owner   User            @relation(fields: [ownerId], references: [id], onDelete: Cascade)
-  servers ProjectServer[]
+  owner          User            @relation(fields: [ownerId], references: [id], onDelete: Cascade)
+  servers        ProjectServer[]
+  prompts        Prompt[]
+  promptRequests PromptRequest[]
 
   @@index([name])
   @@index([ownerId])
@@ -227,6 +230,41 @@ enum InstanceStatus {
   ERROR
 }
 
+// ── Prompts (approved content resources) ──
+
+model Prompt {
+  id        String   @id @default(cuid())
+  name      String
+  content   String   @db.Text
+  projectId String?
+  version   Int      @default(1)
+  createdAt DateTime @default(now())
+  updatedAt DateTime @updatedAt
+
+  project Project? @relation(fields: [projectId], references: [id], onDelete: Cascade)
+
+  @@unique([name, projectId])
+  @@index([projectId])
+}
+
+// ── Prompt Requests (pending proposals from LLM sessions) ──
+
+model PromptRequest {
+  id               String   @id @default(cuid())
+  name             String
+  content          String   @db.Text
+  projectId        String?
+  createdBySession String?
+  createdByUserId  String?
+  createdAt        DateTime @default(now())
+
+  project Project? @relation(fields: [projectId], references: [id], onDelete: Cascade)
+
+  @@unique([name, projectId])
+  @@index([projectId])
+  @@index([createdBySession])
+}
+
 // ── Audit Logs ──
 
 model AuditLog {