C12.0: ElyMail backend moves to Rust crates; iCloud by app password

async-imap, async-pop, mail-send, mail-parser and mail-builder replace
MailCore 2. The MailCore 2 and libetpan fetch, build and probe scripts
go. HTML bodies render as a sanitized block subset in GPUI; compose uses
the Markdown document component. OAuth client IDs come from oauth.env
(ignored) or CI secrets. The task list for C12 is rewritten in order.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

tests/scripts/build-libetpan.sh

@@ -1,37 +0,0 @@
-#!/usr/bin/env bash
-# build-libetpan.sh rebuilds stale caches and shows build errors.
-set -euo pipefail
-
-root=$(cd "$(dirname "$0")/../.." && pwd)
-src=$root/reference/libetpan
-[ -d "$src/.git" ] || { echo "SKIP build-libetpan: reference/libetpan is not checked out"; exit 0; }
-work=$(mktemp -d)
-trap 'rm -rf "$work"' EXIT
-fail() {
-  echo "FAIL: $*" >&2
-  exit 1
-}
-
-mkdir -p "$work/scripts" "$work/engines/libetpan/lib" "$work/reference" "$work/tests/engines"
-cp "$root/scripts/build-libetpan.sh" "$work/scripts/"
-cp "$root/tests/engines/libetpan.sh" "$work/tests/engines/"
-ln -s "$src" "$work/reference/libetpan"
-git -C "$src" rev-parse HEAD >"$work/engines/libetpan/PIN"
-touch "$work/engines/libetpan/lib/libetpan.a"
-: >"$work/engines/libetpan/BUILD-config.h"
-
-if OPENSSL_DIR=/nonexistent "$work/scripts/build-libetpan.sh" >"$work/out" 2>&1; then
-  fail "a cached build without TLS was reused"
-fi
-grep -q "no OpenSSL headers under /nonexistent" "$work/out" || fail "the OpenSSL error was not shown"
-
-if OPENSSL_DIR=/nonexistent "$work/tests/engines/libetpan.sh" >"$work/out" 2>&1; then
-  fail "the probe passed on a TLS-less cached build"
-fi
-grep -q "no OpenSSL headers under /nonexistent" "$work/out" || fail "the probe hid the build error"
-
-printf '#define HAVE_OPENSSL 1\n#define HAVE_JSON 1\n' >"$work/engines/libetpan/BUILD-config.h"
-OPENSSL_DIR=/nonexistent "$work/scripts/build-libetpan.sh" >"$work/out" 2>&1 || fail "a valid cache was not reused"
-grep -q "^ok    libetpan" "$work/out" || fail "a valid cache did not print ok"
-
-echo "build-libetpan: stale caches are rebuilt, errors reach stderr, valid caches are reused"

tests/scripts/references.sh

@@ -4,7 +4,7 @@ set -euo pipefail
 
 root=$(cd "$(dirname "$0")/../.." && pwd)
 script=$root/scripts/fetch-references.sh
-names="Ely-GPUI-Components zed libreoffice-core mupdf git tesseract mailcore2 libetpan marktext colamd magpie agent-client-protocol markion markdown-rs omarchy"
+names="Ely-GPUI-Components zed libreoffice-core mupdf git tesseract marktext colamd magpie agent-client-protocol markion markdown-rs omarchy"
 
 fail() {
   echo "FAIL: $*" >&2
@@ -26,10 +26,7 @@ for header in \
   libreoffice-core/include/LibreOfficeKit/LibreOfficeKit.h \
   mupdf/include/mupdf/fitz.h \
   mupdf/thirdparty/freetype/include/freetype/freetype.h \
-  tesseract/include/tesseract/capi.h \
-  mailcore2/CMakeLists.txt \
-  libetpan/src/low-level/gmail/mailgmail.h \
-  libetpan/src/low-level/activesync/mailactivesync.h; do
+  tesseract/include/tesseract/capi.h; do
   [ -s "$root/reference/$header" ] || fail "missing reference/$header"
 done
 
@@ -37,12 +34,10 @@ want=$(printf '%s\n' desktop/inc desktop/source/lib include/LibreOfficeKit libre
 have=$(git -C "$root/reference/libreoffice-core" sparse-checkout list | sort)
 [ "$have" = "$want" ] || fail "libreoffice-core sparse set differs: $have"
 
-for name in mupdf mailcore2; do
-  status=$(git -C "$root/reference/$name" submodule status --recursive)
-  [ -n "$status" ] || fail "$name lists no submodules"
-  bad=$(grep '^[-+U]' <<<"$status" || true)
-  [ -z "$bad" ] || fail "$name submodules off their pins: $bad"
-done
+status=$(git -C "$root/reference/mupdf" submodule status --recursive)
+[ -n "$status" ] || fail "mupdf lists no submodules"
+bad=$(grep '^[-+U]' <<<"$status" || true)
+[ -z "$bad" ] || fail "mupdf submodules off their pins: $bad"
 
 grep -q "rev = \"$(pin_of Ely-GPUI-Components)\"" "$root/Cargo.toml" ||
   fail "the component library pin differs from the workspace's"