feat: add structured prompt invocation backend

- parse prompt tools metadata and carry structured promptInvocation payloads
- store prompt invocation metadata on trigger messages for replay-safe reruns
- route prompt agents through per-turn plan or Copilot agent overrides
- restrict prompt-scoped tools in sidecar session configuration
- auto-rescan project customization files with debounced watchers
- document the new customization watcher and prompt invocation flow

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

src/shared/domain/projectCustomization.ts

@@ -37,11 +37,22 @@ export interface ProjectPromptFile {
   name: string;
   description?: string;
   agent?: string;
+  tools?: string[];
   template: string;
   variables: ProjectPromptVariable[];
   sourcePath: string;
 }
 
+export interface ProjectPromptInvocation {
+  id: string;
+  name: string;
+  sourcePath: string;
+  resolvedPrompt: string;
+  description?: string;
+  agent?: string;
+  tools?: string[];
+}
+
 export interface ProjectCustomizationState {
   instructions: ProjectInstructionFile[];
   agentProfiles: ProjectAgentProfile[];
@@ -262,9 +273,54 @@ function normalizeProjectPromptFile(promptFile: ProjectPromptFile): ProjectPromp
     normalizedPromptFile.agent = agent;
   }
 
+  const tools = normalizeOptionalStringArray(promptFile.tools);
+  if (tools) {
+    normalizedPromptFile.tools = tools;
+  }
+
   return normalizedPromptFile;
 }
 
+export function normalizeProjectPromptInvocation(
+  promptInvocation?: ProjectPromptInvocation,
+): ProjectPromptInvocation | undefined {
+  if (!promptInvocation) {
+    return undefined;
+  }
+
+  const normalizedPromptInvocation: ProjectPromptInvocation = {
+    id: promptInvocation.id.trim(),
+    name: promptInvocation.name.trim(),
+    sourcePath: normalizePathLikeString(promptInvocation.sourcePath),
+    resolvedPrompt: promptInvocation.resolvedPrompt.trim(),
+  };
+
+  if (
+    normalizedPromptInvocation.id.length === 0
+    || normalizedPromptInvocation.name.length === 0
+    || normalizedPromptInvocation.resolvedPrompt.length === 0
+  ) {
+    return undefined;
+  }
+
+  const description = normalizeOptionalString(promptInvocation.description);
+  if (description) {
+    normalizedPromptInvocation.description = description;
+  }
+
+  const agent = normalizeOptionalString(promptInvocation.agent);
+  if (agent) {
+    normalizedPromptInvocation.agent = agent;
+  }
+
+  const tools = normalizeOptionalStringArray(promptInvocation.tools);
+  if (tools) {
+    normalizedPromptInvocation.tools = tools;
+  }
+
+  return normalizedPromptInvocation;
+}
+
 function compareProjectFiles(
   left: Pick<ProjectInstructionFile | ProjectAgentProfile | ProjectPromptFile, 'sourcePath' | 'id'>,
   right: Pick<ProjectInstructionFile | ProjectAgentProfile | ProjectPromptFile, 'sourcePath' | 'id'>,

src/shared/domain/session.ts

@@ -16,6 +16,10 @@ import type { PendingPlanReviewRecord } from '@shared/domain/planReview';
 import type { PendingMcpAuthRecord } from '@shared/domain/mcpAuth';
 import type { ChatMessageAttachment } from '@shared/domain/attachment';
 import type { InteractionMode } from '@shared/contracts/sidecar';
+import {
+  normalizeProjectPromptInvocation,
+  type ProjectPromptInvocation,
+} from '@shared/domain/projectCustomization';
 
 export type ChatRole = 'system' | 'user' | 'assistant';
 export type ChatMessageKind = 'response' | 'thinking';
@@ -38,6 +42,7 @@ export interface ChatMessageRecord {
   isPinned?: boolean;
   pending?: boolean;
   attachments?: ChatMessageAttachment[];
+  promptInvocation?: ProjectPromptInvocation;
 }
 
 export interface SessionBranchOrigin {
@@ -166,6 +171,20 @@ export function resolveSessionModelConfig(
   };
 }
 
+export function normalizeChatMessageRecord(message: ChatMessageRecord): ChatMessageRecord {
+  const normalizedMessage: ChatMessageRecord = {
+    ...message,
+  };
+  const promptInvocation = normalizeProjectPromptInvocation(message.promptInvocation);
+  if (promptInvocation) {
+    normalizedMessage.promptInvocation = promptInvocation;
+  } else {
+    delete normalizedMessage.promptInvocation;
+  }
+
+  return normalizedMessage;
+}
+
 export function applySessionModelConfig(
   pattern: PatternDefinition,
   session: SessionRecord,

src/shared/domain/sessionLibrary.ts

@@ -1,6 +1,10 @@
 import type { PatternDefinition } from '@shared/domain/pattern';
 import { isScratchpadProject, type ProjectRecord } from '@shared/domain/project';
 import type { ChatMessageAttachment } from '@shared/domain/attachment';
+import {
+  normalizeProjectPromptInvocation,
+  type ProjectPromptInvocation,
+} from '@shared/domain/projectCustomization';
 import {
   resolveSessionTitle,
   type ChatMessageRecord,
@@ -175,11 +179,26 @@ function cloneAttachments(attachments?: ChatMessageAttachment[]): ChatMessageAtt
   return cloned && cloned.length > 0 ? cloned : undefined;
 }
 
+function clonePromptInvocation(
+  promptInvocation?: ProjectPromptInvocation,
+): ProjectPromptInvocation | undefined {
+  const cloned = normalizeProjectPromptInvocation(promptInvocation);
+  if (!cloned) {
+    return undefined;
+  }
+
+  return {
+    ...cloned,
+    tools: cloned.tools ? [...cloned.tools] : undefined,
+  };
+}
+
 function cloneChatMessageRecord(message: ChatMessageRecord): ChatMessageRecord {
   return {
     ...message,
     pending: false,
     attachments: cloneAttachments(message.attachments),
+    promptInvocation: clonePromptInvocation(message.promptInvocation),
   };
 }
 
@@ -386,6 +405,7 @@ export function editAndResendSessionRecord(
 
   editedMessage.content = content;
   editedMessage.attachments = cloneAttachments(attachments);
+  editedMessage.promptInvocation = undefined;
 
   return {
     ...createDerivedSessionRecord(session, sessionId, editedAt),