feat(FN-2133): standardize project memory path guidance to .fusion/memory/

- Update executor, reviewer, core prompt templates, and path-boundary messaging to reference the .fusion/memory/ directory instead of a single MEMORY.md file
- Broaden worktree boundary checks in pi path validation to allow .fusion/memory/ directory access from task worktrees
- Align memory backend metadata and dashboard backend labels to display file backend storage as .fusion/memory/
- Refresh core/engine tests to assert the new directory-based memory wording and boundary behavior

packages/core/src/agent-prompts.test.ts

@@ -154,7 +154,7 @@ describe("resolveAgentPrompt", () => {
 
   it("built-in executor prompt mentions memory exception", () => {
     const result = resolveAgentPrompt("executor");
-    expect(result).toContain(".fusion/memory/MEMORY.md");
+    expect(result).toContain(".fusion/memory/");
   });
 
   it("built-in executor prompt mentions attachments exception", () => {
@@ -183,7 +183,7 @@ describe("resolveAgentPrompt", () => {
     };
 
     const result = resolveAgentPrompt("executor", config);
-    expect(result).toContain(".fusion/memory/MEMORY.md");
+    expect(result).toContain(".fusion/memory/");
   });
 
   it("senior-engineer prompt mentions attachments exception", () => {

packages/core/src/agent-prompts.ts

@@ -108,7 +108,7 @@ model, read-only access) to independently assess your work.
 You are running in an **isolated git worktree**. This means:
 
 - **All code changes must be made inside the current worktree directory.** Do not modify files outside the worktree — the worktree is your isolated execution environment.
-- **Exception — Project memory:** You MAY read and write to .fusion/memory/MEMORY.md at the project root to save durable project learnings (architecture patterns, conventions, pitfalls).
+- **Exception — Project memory:** You MAY read and write to files under .fusion/memory/ at the project root to save durable project learnings (architecture patterns, conventions, pitfalls).
 - **Exception — Task attachments:** You MAY read files under .fusion/tasks/{taskId}/attachments/ at the project root for context screenshots and documents attached to this task.
 - **Shell commands** run inside the worktree by default. Avoid using cd to navigate outside the worktree.
 
@@ -519,7 +519,7 @@ model, read-only access) to independently assess your work.
 You are running in an **isolated git worktree**. This means:
 
 - **All code changes must be made inside the current worktree directory.** Do not modify files outside the worktree — the worktree is your isolated execution environment.
-- **Exception — Project memory:** You MAY read and write to .fusion/memory/MEMORY.md at the project root to save durable project learnings (architecture patterns, conventions, pitfalls).
+- **Exception — Project memory:** You MAY read and write to files under .fusion/memory/ at the project root to save durable project learnings (architecture patterns, conventions, pitfalls).
 - **Exception — Task attachments:** You MAY read files under .fusion/tasks/{taskId}/attachments/ at the project root for context screenshots and documents attached to this task.
 - **Shell commands** run inside the worktree by default. Avoid using cd to navigate outside the worktree.
 

packages/core/src/memory-backend.test.ts

@@ -85,7 +85,7 @@ describe("memory-backend", () => {
 
       it("should have human-readable name", () => {
         const backend = new FileMemoryBackend();
-        expect(backend.name).toBe("File (.fusion/memory/MEMORY.md)");
+        expect(backend.name).toBe("File (.fusion/memory/)");
       });
     });
 

packages/core/src/memory-backend.ts

@@ -215,7 +215,7 @@ const backendRegistry = new Map<string, MemoryBackend>();
  */
 export class FileMemoryBackend implements MemoryBackend {
   readonly type = "file";
-  readonly name = "File (.fusion/memory/MEMORY.md)";
+  readonly name = "File (.fusion/memory/)";
   readonly capabilities: MemoryBackendCapabilities = {
     readable: true,
     writable: true,

packages/core/src/types.ts

@@ -1276,15 +1276,15 @@ export interface ProjectSettings {
    *  Extraction only runs if BOTH this time has elapsed AND memory has grown
    *  by more than MIN_INSIGHT_GROWTH_CHARS characters. Default: 86400000 (24h). */
   insightExtractionMinIntervalMs?: number;
-  /** When enabled, agents will consult and update .fusion/memory/MEMORY.md with durable
+  /** When enabled, agents will consult and update files under .fusion/memory/ with durable
    *  project learnings. When disabled, agents will not include memory instructions
-   *  in their prompts and will not read or write to .fusion/memory/MEMORY.md.
+   *  in their prompts and will not read or write to .fusion/memory/ files.
    *  Default: true (enabled for backward compatibility). */
   memoryEnabled?: boolean;
   /** Memory backend type for pluggable memory storage.
    *  Available built-in backends:
    *  - "qmd": QMD (Quantized Memory Distillation) backend using the qmd CLI tool (default)
-   *  - "file": File-based backend storing memory in `.fusion/memory/MEMORY.md`
+   *  - "file": File-based backend storing memory in `.fusion/memory/`
    *  - "readonly": Read-only backend that returns empty memory (for external management)
    *  - Any registered custom backend type
    *  Default: "qmd" */