feat(#90): IMP-56 u1-u19 catch-up before final close (post-u20 push fix)

u1: text_overrides axis in user_overrides_io
u2: structure_overrides axis in user_overrides_io
u3: vite allowlist for new endpoints
u4: text_override_resolver
u5: Step 12 text_overrides apply in phase_z2_pipeline
u6: structure_override_resolver
u7: text_path_stamper
u8: SlideCanvas text-edit capture
u9: SlideCanvas structure-edit overlay
u10: userOverridesApi service extension
u11: designAgent types extension
u12: slidePlanUtils restore
u13: user_overrides endpoint tests
u14: user_overrides restore tests
u15: pipeline fallback tests
u16: edit-mode state + gating tests
u17: slide_base print mode CSS
u18: /api/connect endpoint (vite)
u19: /api/export endpoint (vite)

Recovery scope: 29 files (12 modified + 17 new). u20 already pushed in
9439575; this commit lands u1-u19 that were authored but not committed
before #90 was externally closed.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Front/client/tests/user_overrides_endpoint.test.ts

@@ -305,23 +305,37 @@ describe("handleGetUserOverrides (IMP-52 u3)", () => {
 // IMP-52 u4 — PUT endpoint coverage
 // ---------------------------------------------------------------------------
 
-describe("KNOWN_USER_OVERRIDES_AXES (IMP-52 u4)", () => {
+describe("KNOWN_USER_OVERRIDES_AXES (IMP-52 u4 + IMP-56 #90 u3 allowlist sync)", () => {
   it("matches the Python KNOWN_AXES tuple in src/user_overrides_io.py", () => {
     // The on-disk schema is shared with backend pipeline fallback (u2).
     // Any drift here means a PUT could write an axis that the Python
     // load() ignores, or vice-versa, silently losing user overrides.
-    // Mirror is Python-minus-`slide_css` (known IMP-45 #74 gap — the
-    // frontend never writes slide_css). IMP-55 #93 u1 adds the bool
-    // `manual_section_assignment` axis as a first-class allowlist entry.
+    // IMP-56 #90 u3 closes the prior `slide_css` gap (IMP-45 #74) and
+    // pre-wires `text_overrides` (IMP-56 #90 u1) +
+    // `structure_overrides` (IMP-56 #90 u2) — full 9-axis mirror of the
+    // Python tuple, same order.
     expect(KNOWN_USER_OVERRIDES_AXES).toEqual([
       "layout",
       "zone_geometries",
       "zone_sections",
       "frames",
       "image_overrides",
+      "slide_css",
       "manual_section_assignment",
+      "text_overrides",
+      "structure_overrides",
     ]);
   });
+
+  it("includes the 3 axes added by IMP-56 #90 u3 (allowlist sync)", () => {
+    // Spot-check the diff in addition to the full-equality assertion so a
+    // future edit that drops one of the new axes fails with a localized
+    // error rather than a 9-vs-N tuple-diff that obscures intent.
+    expect(KNOWN_USER_OVERRIDES_AXES).toContain("slide_css");
+    expect(KNOWN_USER_OVERRIDES_AXES).toContain("text_overrides");
+    expect(KNOWN_USER_OVERRIDES_AXES).toContain("structure_overrides");
+    expect(KNOWN_USER_OVERRIDES_AXES.length).toBe(9);
+  });
 });
 
 describe("mergeUserOverrides (IMP-55 #93 u1) — manual_section_assignment bool axis", () => {