feat: copier update v0.9.0 — extraction docs, state tracking, architecture guides

Sync template from 29ac25b → v0.9.0 (29 template commits). Due to
template's _subdirectory migration, new files were manually rendered
rather than auto-merged by copier.

New files:
- .claude/CLAUDE.md + coding_philosophy.md (agent instructions)
- extract utils.py: SQLite state tracking for extraction runs
- extract/transform READMEs: architecture & pattern documentation
- infra/supervisor: systemd service + orchestration script
- Per-layer model READMEs (raw, staging, foundation, serving)

Also fixes copier-answers.yml (adds 4 feature toggles, removes stale
payment_provider key) and scopes CLAUDE.md gitignore to root only.

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

infra/supervisor/supervisor.sh

@@ -0,0 +1,47 @@
+#!/bin/sh
+# Padelnomics Supervisor — continuous pipeline orchestration.
+# Inspired by TigerBeetle's CFO supervisor: simple, resilient, easy to understand.
+# https://github.com/tigerbeetle/tigerbeetle/blob/main/src/scripts/cfo_supervisor.sh
+#
+# Environment variables (set in systemd EnvironmentFile or .env):
+#   LANDING_DIR        — local path for extracted landing data
+#   DUCKDB_PATH        — path to DuckDB lakehouse file
+#   ALERT_WEBHOOK_URL  — optional ntfy.sh / Slack / Telegram webhook for failures
+
+set -eu
+
+readonly REPO_DIR="/opt/padelnomics"
+
+while true
+do
+    (
+        if ! [ -d "$REPO_DIR/.git" ]; then
+            echo "Repository not found at $REPO_DIR — bootstrap required!"
+            exit 1
+        fi
+
+        cd "$REPO_DIR"
+
+        # Pull latest code
+        git fetch origin master
+        git switch --discard-changes --detach origin/master
+        uv sync
+
+        # Extract
+        LANDING_DIR="${LANDING_DIR:-/data/padelnomics/landing}" \
+        DUCKDB_PATH="${DUCKDB_PATH:-/data/padelnomics/lakehouse.duckdb}" \
+            uv run --package padelnomics_extract extract
+
+        # Transform
+        LANDING_DIR="${LANDING_DIR:-/data/padelnomics/landing}" \
+        DUCKDB_PATH="${DUCKDB_PATH:-/data/padelnomics/lakehouse.duckdb}" \
+            uv run --package sqlmesh_padelnomics sqlmesh run --select-model "serving.*"
+
+    ) || {
+        if [ -n "${ALERT_WEBHOOK_URL:-}" ]; then
+            curl -s -d "Padelnomics pipeline failed at $(date)" \
+                "$ALERT_WEBHOOK_URL" 2>/dev/null || true
+        fi
+        sleep 600  # back off 10 min on failure
+    }
+done