refactor(agents): migrate .agent/ planning tree to .agents/

Standardize on the .agents/ directory (shared with project skills):
phases/, user_stories/, reports/, screenshots/, validate.sh, and
phase-sessions/ + pipeline.log all move to .agents/ (git mv preserves
history; runtime artifacts move alongside).

Updates every reference in AGENTS.md, README.md, .gitignore, app
docstrings, and test story headers. Historical KB content in data/
and the runtime pipeline.log transcript are left untouched.

.agents/validate.sh

@@ -0,0 +1,48 @@
+#!/usr/bin/env bash
+# .agents/validate.sh — validation gate for the phased-execution pipeline.
+#
+# A phase is only moved to .agents/phases/complete/ if this script exits 0.
+# Project adaptation (brain_of_reese — AGENTS.md rule 9, PLAN §10):
+#   1. unit + integration tests with coverage on app/ (floor: >90%)
+#   2. ruff (lint)
+#   3. pyright (types)
+# The per-story Playwright E2E gate (one file per story, run in isolation)
+# is driven by each task file and is NOT part of this gate.
+set -uo pipefail
+cd "$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)"
+rc=0
+
+# ---- 1. unit + integration tests; coverage floor app/ > 90% ----
+pytest_out="$(mktemp)"
+trap 'rm -f "$pytest_out"' EXIT
+if uv run pytest --cov=app --cov-report=term -q >"$pytest_out" 2>&1; then
+  cat "$pytest_out"
+  total_pct="$(awk '/^TOTAL/ {p = $NF} END {print p}' "$pytest_out" | tr -d '%')"
+  if [[ -n "$total_pct" ]] && awk -v p="$total_pct" 'BEGIN { exit !(p > 90) }'; then
+    echo "coverage gate: app/ ${total_pct}% (>90%) OK"
+  else
+    echo "coverage gate FAILED: app/ coverage ${total_pct:-unknown}% (floor >90%)"
+    rc=1
+  fi
+else
+  cat "$pytest_out"
+  echo "tests FAILED: unit + integration suite did not pass"
+  rc=1
+fi
+
+# ---- 2. lint ----
+if ! uv run ruff check .; then
+  rc=1
+fi
+
+# ---- 3. types ----
+if ! uv run pyright; then
+  rc=1
+fi
+
+if [[ $rc -ne 0 ]]; then
+  echo "validation FAILED (see output above)"
+else
+  echo "validation OK"
+fi
+exit "$rc"