docs: harden agent parity rule — all platforms in same change, no exceptions

- CODING_GUIDELINES.md: tighten parity rule wording to match Mike's intent:
  "add feature X" means Windows + Linux + macOS in the same commit
- memory: add feedback_gururmm_agent_parity for future session enforcement

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.claude/CODING_GUIDELINES.md

@@ -128,10 +128,10 @@ A feature that silently no-ops on one platform is a gap, not a cross-platform im
 
 ### The rule
 
-> If you add or change a feature in the agent and the change is not blocked by OS-level APIs,
+> "Add feature X to the agent" means Windows + Linux + macOS. All three, in the same change.
-> you must implement or stub it on all three platforms in the same PR.
+> No exceptions for convenience. If a real implementation is not feasible on a given platform,
-> If a real implementation is not feasible, add a `// TODO(platform): <os> — <reason>` comment
+> add a working stub and a `// TODO(platform): <os> — <reason>` comment in the same commit.
-> and open a tracking item.
+> A feature that silently no-ops on one platform without a stub and TODO is a bug, not a gap.
 
 ### cfg gating — choose the right target
 

.claude/memory/MEMORY.md

@@ -22,6 +22,7 @@
 - [Howard Enos](user_howard.md) — Mike's brother, technician, full trust/access. Known machine: ACG-TECH03L.
 
 ## Feedback
+- [GuruRMM agent parity rule](feedback_gururmm_agent_parity.md) — "Add feature X to the agent" = Windows + Linux + macOS in the same change, no exceptions. Stub + TODO if real impl not feasible.
 - [D2TESTNAS SSH Access](feedback_d2testnas_ssh.md) - Use root@192.168.0.9 with Paper123!@#, not sysadmin
 - [Bypass Permissions Setting](feedback_bypass_permissions_setting.md) - Set permissions.defaultMode to bypassPermissions in settings.json on all machines
 - [365 Remediation Tool](feedback_365_remediation_tool.md) - Always means Graph API app fabb3421, not CIPP

.claude/memory/feedback_gururmm_agent_parity.md

@@ -0,0 +1,16 @@
+---
+name: feedback_gururmm_agent_parity
+description: "Add feature X to the agent" means all three platforms (Windows + Linux + macOS) in the same change — no exceptions
+metadata:
+  type: feedback
+---
+
+"Add feature X to the agent" means Windows + Linux + macOS. All three in the same change.
+
+**Why:** Mike stated this explicitly 2026-05-15. Delivering Windows-only and leaving Linux/macOS for later is not acceptable — it's the same as not finishing the task.
+
+**How to apply:** When implementing any agent feature:
+- If the implementation differs by platform, write all three variants.
+- If a real implementation is not feasible on a platform yet, add a working stub + `// TODO(platform): <os> — <reason>` in the same commit.
+- A silent no-op without a stub and TODO is treated as a bug.
+- See `.claude/CODING_GUIDELINES.md` "GuruRMM Agent — Platform Parity" for the full matrix and known gaps.