feat: harden send preview idempotency

docs/current-status-card.md

@@ -30,7 +30,7 @@ Remote base before local roadmap commits: `b2d839e Merge branch 'codex/n15-repor
 - `isphere_receive_messages` accepts the read-contract argument set for the current local-readonly path: `conversation_id`, `query`, `since`, `limit`, `include_attachment_metadata`, `source_preference`, `preview`, and empty `cursor`.
 - `isphere_search_contacts` and `isphere_search_groups` accept and validate the safe search-contract args for the current local-readonly path and can optionally enrich results from the env-configured C29 `MsgLib.db` display-entity reader; default behavior remains log/JID-backed when MsgLib env vars are absent.
 - `isphere_receive_files` list mode accepts and validates the safe file-list contract args for the current local-readonly path while keeping download blocked.
-- `isphere_send_message` accepts the R6b preview/dry-run contract (`target_type`, `target_id`, `content_text`, `content_sha256`, `idempotency_key`, `execution_mode`) and returns planned preview metadata plus redacted audit metadata; `execution_mode="production"` returns blocked status with all side-effect flags false.
+- `isphere_send_message` accepts the R6b/R6e preview/dry-run contract (`target_type`, `target_id`, `content_text`, `content_sha256`, `idempotency_key`, `execution_mode`) and returns planned preview metadata plus redacted audit/idempotency metadata; `execution_mode="production"` returns blocked status with all side-effect flags false.
 - `native/MsgLibReadSidecar` provides a bounded x86 .NET read-only boundary for `MsgLib.db` schema/display-source checks, bounded contact/group display-entity reads, message-source metadata, and sidecar-level bounded message listing; `internal/msglib` wraps it from Go, C30 wires display metadata as an optional MCP contact/group enrichment source, C39 adds a Go receive-source adapter around `ListMessages`, C40 adds tool-level explicit `msglib_readonly` source selection, and C41 wires it through env configuration without changing the MCP default source.
 - N12-pre and N12R documents define safe offline evidence intake and internal-sandbox live UIA capture procedures.
 - N13/N14/N15 produced selector catalog/report validation infrastructure, but those are supporting validation assets only.
@@ -58,7 +58,7 @@ N13/N14/N15 are pre-business validation results. They can help identify UI eleme
 
 ## Current loop
 
-Current loop: `R6d partial returned sandbox evidence intake accepted for limited use; next R6e sandbox-only send connector shell and idempotency audit hardening`.
+Current loop: `R6e sandbox-only send connector shell and idempotency audit hardening implemented; next R6f fake/sandbox connector contract or corrected full evidence intake`.
 
 Plan file: `docs/superpowers/plans/2026-07-10-core-business-capabilities-roadmap.md`.
 
@@ -118,6 +118,7 @@ Current loop output so far:
 45. R6c: because the local machine cannot log in, prepared an online/internal sandbox evidence package instead of attempting local send. Added `scripts/package-send-sandbox-gate.ps1`, `scripts/verify-send-sandbox-gate-package.ps1`, and `docs/source-discovery/2026-07-10-send-sandbox-gate.md`; local verification generates `runs/send-sandbox-gate-package.zip` with the read-only recorder, before/after scripts, sandbox input template, SHA256 helper, expected-return checklist, and return-zip helper.
 46. R6c package consolidation: upgraded `runs/send-sandbox-gate-package.zip` into a one-pass operator recording suite with `RUN-RECORDING-SUITE.bat`, numbered `01/02/03` scripts, and `RECORDING-PACKAGE-MANIFEST.json`; added a second offline-safe `runs/send-capability-test-package.zip` with `isphere-capability-smoke.exe` plus packaged `ISphereWinHelper.exe` to verify the 9-tool MCP surface, receive/search/file-list fixture behavior, send preview, and `production_send_enabled=false`.
 47. R6d partial intake: accepted `C:\Users\zhaoy\Downloads\1631.zip` as partial evidence only. Added `scripts\validate-returned-send-sandbox-package.ps1`, `scripts\test-validate-returned-send-sandbox-package.ps1`, and `docs/source-discovery/2026-07-10-returned-send-sandbox-analysis.md`. Validator reports `partial_evidence_usable=true` and `r6d_gate_pass=false`: capability test passed, content hash matched, idempotency key/success/no-second-send fields were present, but after-recorder output and manual send timestamps are missing. This can unblock sandbox-only connector-shell/idempotency work, not production send.
+48. R6e: hardened `isphere_send_message` with a sandbox-only connector shell marker and idempotency store. Preview remains no-send; production remains blocked. Duplicate idempotency keys for the same target/content are detected and reported; conflicting reuse of the same idempotency key for different content/target is blocked with all side-effect flags false. `ISPHERE_SEND_IDEMPOTENCY_PATH` can point to a JSONL state file; standard verification uses per-run temporary state.
 
 ## Recompiled business roadmap
 
@@ -213,3 +214,12 @@ R6d partial returned sandbox evidence intake is complete:
 - `partial_evidence_usable=true`: use it to continue sandbox-only send connector shell and idempotency/audit hardening.
 - `r6d_gate_pass=false`: do not enable production `isphere_send_message`, because after-recorder output and manual send timestamps are missing.
 - Next node: R6e sandbox-only send connector shell and idempotency audit hardening.
+
+R6e sandbox-only send connector shell and idempotency audit hardening is complete:
+
+- Added `SendMessageIdempotencyStore` and file-backed `ISPHERE_SEND_IDEMPOTENCY_PATH`.
+- `isphere_send_message` response now exposes `connector_mode="sandbox-only-shell"` and `production_send_enabled=false`.
+- Duplicate same-key/same-target/same-content preview calls return structured metadata with `duplicate_detected=true` and no side effects.
+- Same idempotency key reused for different target/content returns `send_status="blocked"` with `conflict_detected=true` and no side effects.
+- `scripts\verify-go-mcp.ps1` and `cmd\isphere-capability-smoke` use fresh per-run idempotency state to keep repeatable smoke deterministic.
+- Next node: R6f fake/sandbox connector contract or corrected full evidence intake.