fix(framework/tools): wrapper body-safety + login-resolution hardening (#559, #560)

#559 — Markdown body safety / eval removal:
- Add test-issue-create-body-safety.sh: feeds a hostile Markdown body
  ($(...), backticks, quotes, $vars, pipes) through issue-create.sh and
  asserts no command substitution runs and the body reaches tea verbatim.
- Convert issue-comment.sh from unquoted $(get_gitea_repo_args) word-splitting
  to an argv array with an explicit loud login-resolution error.
- Confirmed: zero eval usages remain across tools/git/*.sh; the other
  body-carrying wrappers (issue-create, pr-create, issue-edit, issue-assign)
  already use argv arrays.

#560 — host-derived Gitea login + loud failure:
- detect-platform.sh: add print_gitea_login_diagnostic and emit it on the
  get_gitea_login_for_host failure path (stderr only) — names the unresolved
  host, lists available tea logins, and gives the GITEA_LOGIN override +
  tea-login-add fix. Replaces the previous silent failure.
- Extend test-gitea-login-resolution.sh: assert the diagnostic fires and lists
  logins, login is derived from origin host for both mosaicstack and usc (scoped
  second tea mock), and a valid GITEA_LOGIN override is honored.

Also gitignore the .mosaic-test-work/ shell-harness scratch dir.
Scope: wrapper surface only. All wrapper test harnesses pass locally.

packages/mosaic/framework/tools/git/test-gitea-login-resolution.sh

@@ -230,4 +230,81 @@ if grep -q -- 'tea issue close 536 .*--login mosaicstack' "$LOG_FILE"; then
     exit 1
 fi
 
+# ---------------------------------------------------------------------------
+# #560: loud diagnostic + host-derived login for BOTH instances + override-wins
+# ---------------------------------------------------------------------------
+
+# Loud diagnostic: a host with no matching tea login must emit an actionable
+# error to stderr (the previous behavior was a SILENT failure). The original
+# mock defines only usc/evil-usc logins, so mosaicstack resolution fails here.
+git -C "$REPO_DIR" remote set-url origin https://git.mosaicstack.dev/mosaicstack/stack.git
+diag_stderr=$(run_in_repo bash -c '
+    source "'"$SCRIPT_DIR"'/detect-platform.sh"
+    get_gitea_login_for_host git.mosaicstack.dev
+' 2>&1 1>/dev/null || true)
+if ! grep -q "no Gitea tea login matches host 'git.mosaicstack.dev'" <<<"$diag_stderr"; then
+    echo "Expected loud diagnostic naming the unresolved host; got: $diag_stderr" >&2
+    exit 1
+fi
+if ! grep -q "Available tea logins:" <<<"$diag_stderr"; then
+    echo "Expected diagnostic to list available tea logins; got: $diag_stderr" >&2
+    exit 1
+fi
+
+# Both-instance host derivation + override-wins, using a mock that DOES define a
+# mosaicstack login. Scoped to this section so the API-fallback assertions above
+# (which rely on mosaicstack having NO tea login) remain valid.
+BIN_DIR2="$WORK_DIR/bin2"
+mkdir -p "$BIN_DIR2"
+cp "$BIN_DIR/curl" "$BIN_DIR2/curl"
+cat > "$BIN_DIR2/tea" <<'SH'
+#!/usr/bin/env bash
+set -euo pipefail
+if [[ "$*" == "login list --output json" ]]; then
+    cat <<'JSON'
+[
+  {"name":"mosaicstack","url":"https://git.mosaicstack.dev","user":"jason.woltje"},
+  {"name":"usc","url":"https://git.uscllc.com","user":"jason.woltje"}
+]
+JSON
+    exit 0
+fi
+printf 'tea %s\n' "$*" >> "$MOSAIC_TEST_LOG"
+exit 0
+SH
+chmod +x "$BIN_DIR2/tea"
+
+run_in_repo2() {
+    (
+        cd "$REPO_DIR"
+        PATH="$BIN_DIR2:$PATH" \
+        MOSAIC_CREDENTIALS_FILE="$CREDENTIALS_FILE" \
+        MOSAIC_TEST_LOG="$LOG_FILE" \
+        "$@"
+    )
+}
+
+git -C "$REPO_DIR" remote set-url origin https://git.mosaicstack.dev/mosaicstack/stack.git
+mosaic_login=$(run_in_repo2 bash -c 'source "'"$SCRIPT_DIR"'/detect-platform.sh"; get_gitea_login')
+if [[ "$mosaic_login" != "mosaicstack" ]]; then
+    echo "Expected mosaicstack origin to derive login 'mosaicstack'; got '$mosaic_login'" >&2
+    exit 1
+fi
+
+git -C "$REPO_DIR" remote set-url origin https://git.uscllc.com/USC/uconnect.git
+usc_login_derived=$(run_in_repo2 bash -c 'source "'"$SCRIPT_DIR"'/detect-platform.sh"; get_gitea_login')
+if [[ "$usc_login_derived" != "usc" ]]; then
+    echo "Expected usc origin to derive login 'usc'; got '$usc_login_derived'" >&2
+    exit 1
+fi
+
+# Explicit GITEA_LOGIN override is honored when it matches the host.
+git -C "$REPO_DIR" remote set-url origin https://git.mosaicstack.dev/mosaicstack/stack.git
+override_wins=$(run_in_repo2 bash -c 'export GITEA_LOGIN=mosaicstack; source "'"$SCRIPT_DIR"'/detect-platform.sh"; get_gitea_login')
+if [[ "$override_wins" != "mosaicstack" ]]; then
+    echo "Expected valid GITEA_LOGIN override to win on mosaicstack host; got '$override_wins'" >&2
+    exit 1
+fi
+git -C "$REPO_DIR" remote set-url origin https://git.uscllc.com/USC/uconnect.git
+
 echo "Gitea login resolution regression harness passed"