feat: add receive file download preview contract

docs/superpowers/plans/2026-07-10-r6f-r14-continuous-execution-plan.md

@@ -803,19 +803,19 @@ Created `docs/source-discovery/2026-07-10-returned-send-sent-record-diagnostic.m
 - If resolver lacks accepted mapping, response: `ok=false`, `download_status="blocked"`, `blocked_reason_code="file_cache_mapping_missing"`.
 - If resolver has accepted mapping in fixture tests, response: `ok=true`, `download_status="planned"`, no file copy during preview.
 
-- [ ] **Step 1: Write blocked-preview test**
+- [x] **Step 1: Write blocked-preview test**
 
 Add `TestISphereReceiveFilesDownloadPreviewBlockedWithoutMapping`, asserting `blocked_reason_code="file_cache_mapping_missing"` and `file_contents_read=false`.
 
-- [ ] **Step 2: Write planned-preview fixture test**
+- [x] **Step 2: Write planned-preview fixture test**
 
 Add `TestISphereReceiveFilesDownloadPreviewPlannedWithFixtureMapping`, using an injected fixture resolver and asserting `download_status="planned"`, `file_contents_read=false`, and `file_copied=false`.
 
-- [ ] **Step 3: Implement preview contract**
+- [x] **Step 3: Implement preview contract**
 
 Keep non-preview real download blocked unless R10 accepted mapping exists and a separate production-copy gate is added.
 
-- [ ] **Step 4: Verify and commit**
+- [x] **Step 4: Verify and commit**
 
 ```powershell
 git diff --check
@@ -830,6 +830,15 @@ git push gitea main
 
 **Acceptance gate:** 数字员工可以理解“为什么现在不能下载”，并在有映射时得到 planned preview。
 
+
+**R11 Result:**
+
+- Actual implementation files are `internal/tools/isphere_files.go` and `internal/tools/isphere_files_test.go`.
+- Added structured download preview blocked response for missing mapping.
+- Added injected fixture resolver test for planned preview.
+- Standard MCP smoke now reports `receive_file_download_preview_blocked=true`.
+- Real file copy/download remains blocked; preview reads no file contents and returns no raw paths.
+
 ---
 
 ### R12: Receive-message reconciliation helper