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>

governance/README.md

@@ -179,6 +179,7 @@ You might also want, project-permitting:
 - [Q-47: Live mixed documents — implement?](questions/design.md#q-47-live-mixed-documents--implement) — _design_
 - [Q-48: Sealed-workspace mode — implement?](questions/design.md#q-48-sealed-workspace-mode--implement) — _design_
 - [Q-49: Review honorable mentions — which, if any, get promoted?](questions/design.md#q-49-review-honorable-mentions--which-if-any-get-promoted) — _design_
+- [Q-50: Web/WASM target after the dart:ffi pivot — fence, fix, or drop?](questions/architecture.md#q-50-webwasm-target-after-the-dartffi-pivot--fence-fix-or-drop) — _architecture_
 
 ## Resolved questions