machine-docs: move all per-phase coordination files out of repo root

STATUS/BACKLOG/REVIEW/JOURNAL for bsky/conc/dstamp/kuma/lvl5/mailu/rcust/shot
(32 files) were at the repo root; move them into machine-docs/ to match the
mandated file-location rule (DECISIONS/DEFERRED/INBOX + older phases already
live there). AGENTS.md gains an explicit File-location rule. No content change.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

AGENTS.md

@@ -3,6 +3,14 @@
 Working notes for agents (and humans) modifying the cc-ci server. See `README.md` for what the server
 does and `machine-docs/` for the build's living state (`DECISIONS.md`, `DEFERRED.md`, `STATUS-*.md`).
 
+## File-location rule (mandatory)
+
+ALL coordination / loop-state files live under **`machine-docs/`**, NEVER the repo root. That means
+the phase-namespaced `STATUS-*.md`, `BACKLOG-*.md`, `REVIEW-*.md`, `JOURNAL-*.md`, the shared
+`DECISIONS.md` / `DEFERRED.md`, and the `ADVERSARY-INBOX.md` / `BUILDER-INBOX.md` side-channels.
+Create `machine-docs/` if missing; if you ever find one of these at the root, `git mv` it into
+`machine-docs/`. (The repo root is for actual server code/config — `runner/`, `tests/`, `nix/`, etc.)
+
 ## Testing cadence
 
 Two kinds of tests live here — run them on **different** cadences: