a pk- key authenticates nobody, so stop telling readers it reads

The README offered the two key shapes as a permission split — pk- to read,
sk- to write. cloud's own identity boundary says otherwise: middleware_identity
returns nil for any pk- before it consults the key store, because a key meant
for a browser bundle must not read. A pk- resolves to an org so a beacon can be
attributed to a tenant, and that is all it does.

Following the old sentence, a reader exports a pk- and every one of the five
flows answers 403 — /v1/tools spells out why, "a validated principal is
required" — and that refusal reads like a revoked key rather than the wrong
shape of key. examples/client.py now refuses a pk- before the request goes out,
the same argument that already rejects an unsendable access_token.

Also: three status codes in example docstrings had drifted from what the API
answers now (/v1/kv/keys/* 404s on every verb, /v1/automations/mcp 404s), and
two dead files went with them — examples/.keep, whose directory has held real
flows for a while, and scripts/mock, which reads a .stats.yml this repo does
not have and which scripts/test already says is unnecessary.

scripts/mock

@@ -1,41 +0,0 @@
-#!/usr/bin/env bash
-
-set -e
-
-cd "$(dirname "$0")/.."
-
-if [[ -n "$1" && "$1" != '--'* ]]; then
-  URL="$1"
-  shift
-else
-  URL="$(grep 'openapi_spec_url' .stats.yml | cut -d' ' -f2)"
-fi
-
-# Check if the URL is empty
-if [ -z "$URL" ]; then
-  echo "Error: No OpenAPI spec path/url provided or found in .stats.yml"
-  exit 1
-fi
-
-echo "==> Starting mock server with URL ${URL}"
-
-# Run prism mock on the given spec
-if [ "$1" == "--daemon" ]; then
-  npm exec --package=@stainless-api/[email protected] -- prism mock "$URL" &> .prism.log &
-
-  # Wait for server to come online
-  echo -n "Waiting for server"
-  while ! grep -q "✖  fatal\|Prism is listening" ".prism.log" ; do
-    echo -n "."
-    sleep 0.1
-  done
-
-  if grep -q "✖  fatal" ".prism.log"; then
-    cat .prism.log
-    exit 1
-  fi
-
-  echo
-else
-  npm exec --package=@stainless-api/[email protected] -- prism mock "$URL"
-fi