Move readings/ to companion repo, add .env.example, fix README tree

The three readings (maaseh_merkavah, moreh_nevuchim, mishpatim)
are interpretive essays + one parallel Prolog encoding. They are
"the book" the README describes, not the specification or the
implementation. The essays don't influence the shipped code;
mishpatim's Prolog is a parallel encoding to talmudic_engine/
mitzvot.pl, not its source.

Moved to ~/shorashim-readings/ — a companion repo. The code repo
stays spec + implementation + deployment. The book gets its own
home so it can grow without dragging 5,853 verse files with every
essay edit.

Also:
- README.md: rewrote the "Repository Structure" tree to match
  reality (it still showed readings/terumah/, scripts/conversation_
  search.py, memory/, and was missing l1/, AGENTS.md, BUILD_*,
  KOHEN.md, opencode.json, .env.example).
- Added a "Kept outside this repo" section naming the three
  companion directories: shorashim-readings, shorashim-source-data,
  shorashim-operator-notes.
- Updated the "This repository contains" list: readings are no
  longer item 1; the edut (l1/torah/) is now called out explicitly.
- Created .env.example with placeholders for ANTHROPIC_API_KEY,
  GITEA_TOKEN, REGISTRY_CLI_SECRET, and SHORASHIM_SOURCE_DATA.

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

.env.example

@@ -0,0 +1,31 @@
+# shorashim environment variables — template
+#
+# Copy to .env and fill in values.
+# .env is gitignored; .env.example is tracked.
+#
+#   cp .env.example .env
+#
+# Nothing in this file is required to build or test shorashim locally.
+# These are for: pushing code to Gitea, pushing images to the container
+# registry, and authenticating to the gitea-mcp server from scripts.
+
+# --- Anthropic API (optional) ---
+# Used by external tooling that calls Claude. Not required to run shorashim.
+export ANTHROPIC_API_KEY=sk-ant-api03-REPLACE_ME
+
+# --- Gitea Personal Access Token ---
+# Used to push code from your workstation and to authenticate the
+# gitea-mcp server to the backend Gitea instance.
+# Generate at: <gitea-host>/user/settings/applications
+# Grant: repo scope.
+export GITEA_TOKEN=REPLACE_ME
+
+# --- Container Registry CLI Secret ---
+# For `docker login` and `docker push` to the private registry.
+# In Harbor-based registries (like Exoscale), find under User Profile.
+export REGISTRY_CLI_SECRET=REPLACE_ME
+
+# --- Optional: override for build_l1.py ---
+# Path to the raw morphhb source data (the quarry).
+# Default: ~/shorashim-source-data/morphhb
+# export SHORASHIM_SOURCE_DATA=$HOME/shorashim-source-data/morphhb