feat: extract files from message logs

docs/superpowers/plans/2026-07-09-stage-c-log-backed-receive-messages-loop.md

@@ -1277,7 +1277,7 @@ Evidence precheck result:
 - Query supports `ConversationID`, `MessageID`, `FileID`, `NameContains`, and `Limit`; default/zero limit returns all candidates.
 - This loop does not register the MCP tool yet. Registration/list-mode smoke becomes C14 after source behavior passes tests.
 
-- [ ] **Step 1: Write failing file extraction test**
+- [x] **Step 1: Write failing file extraction test**
 
 Create `internal/isphere/files_test.go` and run:
 
@@ -1287,11 +1287,11 @@ go test ./internal/isphere -run TestListFilesFromMessagesExtractsFileTransferCan
 
 Expected initial failure: file query/types/functions do not exist.
 
-- [ ] **Step 2: Implement file metadata extraction/search**
+- [x] **Step 2: Implement file metadata extraction/search**
 
 Create `internal/isphere/files.go` with minimal pure Go logic over normalized messages and synthetic/redacted fixtures.
 
-- [ ] **Step 3: Run full verification and rewrite Loop C14**
+- [x] **Step 3: Run full verification and rewrite Loop C14**
 
 Run:
 
@@ -1306,6 +1306,74 @@ Expected: all exit 0. Remove any generated root `isphere-mcp.exe` after build. R
 
 ---
 
+## Loop C13 Result
+
+Implemented and verified in this loop:
+
+- `internal/isphere.ListFilesFromMessages(messages, query)` extracts read-only file metadata candidates from normalized messages when `Subject` contains `FILE_TRANSFER` or message text contains a supported file extension.
+- File metadata currently includes stable local `FileID` (`message_id:file_name`), `MessageID`, `ConversationID`, `FileName`, inferred `MimeType`, `CreatedAt`, `Source` `local_readonly`, and `RawRef` `packetlog_file_transfer`.
+- `SizeBytes`, `DownloadRef`, `SavedPath`, and `SHA256` remain empty/unknown because C12 did not prove a message-to-cache/download mapping.
+- Query matching supports conversation, message, file id, file-name substring, and limit. Tests use only synthetic/redacted filenames.
+- Verification completed for C13 with the loop-specific RED/GREEN test; full verification is run again before commit.
+
+---
+
+## Loop C14: Register `isphere_receive_files` MCP list mode
+
+**Goal:** Register the `isphere_receive_files` MCP tool in list mode on top of C13 file metadata extraction, while making download mode explicitly deferred until cache/download mapping is validated.
+
+**Planned files:**
+- Create: `internal/tools/isphere_files.go`
+- Create: `internal/tools/isphere_files_test.go`
+- Modify: `internal/mcpserver/server.go`
+- Modify: `internal/mcpserver/server_test.go`
+- Modify: `scripts/verify-go-mcp.ps1`
+- Modify: `docs/go-mcp-runbook.md`
+- Modify: `docs/current-status-card.md`
+- Modify: `docs/source-discovery/capability-source-matrix.md`
+- Modify: `docs/superpowers/plans/2026-07-09-stage-c-log-backed-receive-messages-loop.md`
+
+**Planned interface:**
+- Tool name: `isphere_receive_files`.
+- Input: `conversation_id`, `message_id`, `file_id`, `name_contains`, `mode`, `limit`.
+- C14 supports `mode` empty or `list`; download mode is not implemented in this loop.
+- Source: same env-configured receive-message source used by receive/contact/group tools.
+- Output shape: `ok`, `mode`, `files`, `next_cursor`, and `audit`, aligned with `docs/mcp-core-tools-contract.md`.
+- Default empty source returns `ok: true`, `mode: "list"`, `files: []`.
+
+- [ ] **Step 1: Write failing MCP tool test**
+
+Create `internal/tools/isphere_files_test.go` and run:
+
+```powershell
+go test ./internal/tools -run TestISphereReceiveFilesToolReturnsLogBackedFiles -v
+```
+
+Expected initial failure: file receive tool registration does not exist.
+
+- [ ] **Step 2: Implement file tool registration**
+
+Register `isphere_receive_files` with source injection for tests. Use `ListFilesFromMessages` and return a contract-shaped map with minimal audit metadata.
+
+- [ ] **Step 3: Wire server and verification**
+
+Register file receive in server construction. Update server tool-count tests and `scripts/verify-go-mcp.ps1` to expect eight tools and call `isphere_receive_files` against default empty source and synthetic configured file-transfer fixture.
+
+- [ ] **Step 4: Run full verification and commit**
+
+Run:
+
+```powershell
+git diff --check
+go test ./...
+go build ./cmd/isphere-mcp
+powershell -NoProfile -ExecutionPolicy Bypass -File scripts/verify-go-mcp.ps1
+```
+
+Expected: all exit 0. Remove any generated root `isphere-mcp.exe` after build. Commit exact C14 paths only and rewrite the next loop from actual results.
+
+---
+
 ## Self-Review
 
 - Spec coverage: the plan follows the user's cyclic requirement: plan first, implement one loop at a time, update the next loop after each result, and ask only on blockers.