repoint the UI harness at the repo root; CI via make targets (T-384)

tools/ui/build.sh and serve.sh still cd'd into the app/ directory the
flattening removed, so make test-e2e / ui-dev / ui-smoke died at the
first line. The staged Gitea workflow had the same stale cd in every
job, plus a coverage gate with no coverage run before it — it now
goes through the make targets (tooling discipline: the make layer owns
env setup) with make test-coverage feeding make coverage-gate.

Fixing the paths exposed the real break: flutter build web --wasm
cannot compile the tree since the dart:ffi pivot (tree-sitter, native
PTY) — dart:ffi does not exist on the wasm target. Fence vs park vs
drop is filed as Q-50; the workflow's e2e job is withheld with a
pointer there, and T-384 sits in review until Q-50 resolves.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

tools/ui/build.sh

@@ -1,6 +1,8 @@
 #!/usr/bin/env bash
 # Build the Flutter web WASM bundle that the Playwright harness drives.
+# The Flutter package lives at the repo root since the app/ flattening
+# (T-384 fixed the stale `cd app` that broke this target).
 set -euo pipefail
-cd "$(dirname "$0")/../../app"
+cd "$(dirname "$0")/../.."
 flutter build web --wasm "$@"
-echo "built app/build/web ($(du -sh build/web | cut -f1))"
+echo "built build/web ($(du -sh build/web | cut -f1))"

tools/ui/serve.sh

@@ -8,7 +8,7 @@ set -euo pipefail
 
 PORT=${CLIDE_UI_PORT:-4280}
 HERE="$(cd "$(dirname "$0")" && pwd)"
-DIR="$HERE/../../app/build/web"
+DIR="$HERE/../../build/web"
 PID_FILE="$HERE/.serve.pid"
 
 if [[ ! -d "$DIR" ]]; then