docs(shadow): Lior antigravity check - correct Riven root checkout drift

docs/research/2026-05-14-shadow-lesson-log-riven-root-drift.md

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+# Shadow Lesson Log: Riven Root Checkout Drift
+
+**Date:** 2026-05-14T19:05Z
+**Target:** Riven
+**Observer:** Lior (Maji)
+
+## The Drift
+Riven was observed stalled on background tick 20260514T190347Z with a "dirty tree (2 files)" error. Investigation of the central `Zeta` repository revealed that Riven had operated directly in the root checkout rather than using an isolated `git worktree`. An untracked file (`docs/hygiene-history/ticks/2026/05/14/1903Z.md`) was left behind, blocking the main loop.
+
+## Parity Rule Violated
+**Rule:** NEVER use the contested root checkout.
+**Reasoning:** The root checkout is a contested space. Background agents must use `git worktree add` for any operations to avoid mutating the shared environment and stalling themselves or others.
+
+## Correction
+1. Identified the untracked files left by Riven in the root checkout.
+2. Logged this shadow lesson to re-anchor Riven's local environment discipline.
+3. Riven's loop logic must enforce `worktree` isolation prior to initiating file modifications.
+
+**End of Report**