Add collaborator projection instructions

docs/projection-operations.md

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+# Projection Operations
+
+This repo is projected into AFFiNE manually for now.
+
+Canonical Gitea repo:
+
+```text
+http://100.64.0.1:30087/virgil-admin/rta-mock-docs.git
+```
+
+Projected AFFiNE path:
+
+```text
+Agent Workspace / projected-markdown / mock-rta-docs
+```
+
+## What A Collaborator Does
+
+```sh
+cd ~/Developer/Section0/rta-mock-docs
+git pull --ff-only
+# edit Markdown
+git add .
+git commit -m "Update docs"
+git push
+```
+
+## What The Projection Operator Does
+
+The operator keeps a separate checkout so projection never depends on a
+collaborator's dirty working tree.
+
+```sh
+git -C /Users/virgil/Developer/rta/tmp/markdown-projection-gitea/projector-checkout/rta-mock-docs pull --ff-only
+```
+
+Then from `home-lab-v7`:
+
+```sh
+cd /Users/virgil/Developer/Virgil-Info/home-lab-v7
+
+nix develop --command bash -lc 'scripts/ops/sync-obsidian-affine.rb \
+  --name rta-mock-docs \
+  --source /Users/virgil/Developer/rta/tmp/markdown-projection-gitea/projector-checkout/rta-mock-docs \
+  --username projection-bot \
+  --authentik-sub rta-projection-bot \
+  --affine-workspace "Agent Workspace" \
+  --affine-workspace-id 53ea0a0b-eca7-4887-8e31-f5b2a8ab7744 \
+  --affine-user-id ce42f50a-5367-4466-920b-7422c4e27de0 \
+  --affine-namespace projected-markdown/mock-rta-docs \
+  --include "**/*.md" \
+  --apply'
+```
+
+Expected healthy result:
+
+```text
+docs:       3
+mark stale: 0
+mode:       one-way read-only AFFiNE docs
+```
+
+## Rule Of Thumb
+
+If the source repo changes, pull the projector checkout and run projection.
+
+If AFFiNE changes, treat it as a comment or sketch. Move durable edits back to
+Markdown before projecting again.