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>

src/user_overrides_io.py

@@ -5,10 +5,18 @@ auto-restores user choices without re-clicking. Source of truth = MDX-keyed
 file (stem of the MDX path), NOT ``data/runs/<run_id>/`` which mints a fresh
 run_id per ``/api/run`` invocation.
 
-Schema (7 axes; stable order; IMP-51 #79 u1 added ``image_overrides``;
+Schema (9 axes; stable order; IMP-51 #79 u1 added ``image_overrides``;
 IMP-45 #74 u1 added ``slide_css``; IMP-55 #93 u1 added
 ``manual_section_assignment`` as a bool intent marker so the backend can
-distinguish a user drag-drop from frontend auto-carry zone_sections):
+distinguish a user drag-drop from frontend auto-carry zone_sections;
+IMP-56 #90 u1 added ``text_overrides`` as a Step-22 text-edit persist axis
+keyed by ``{zone_id: {text_path: value}}`` where ``text_path`` is the
+``{slot_key}.{line_index}`` stamp emitted by u8; IMP-56 #90 u2 added
+``structure_overrides`` as a Step-22 structure-edit persist axis keyed by
+``{zone_id: {"slot_order": [<slot_key>, ...], "hidden_slots": [<slot_key>, ...]}}``
+— scope is intentionally LOCKED to slot reorder + hide; frame swap stays
+on the existing ``frames`` axis to prevent the Phase Z regression of
+AI-driven HTML structure mutation):
 
     {
       "layout":                    <string|null>,
@@ -17,7 +25,9 @@ distinguish a user drag-drop from frontend auto-carry zone_sections):
       "frames":                    {<unit_id>: <template_id>},
       "image_overrides":           {<image_id>: {"x": float, "y": float, "w": float, "h": float}},
       "slide_css":                 <string|null>,
-      "manual_section_assignment": <bool>
+      "manual_section_assignment": <bool>,
+      "text_overrides":            {<zone_id>: {<text_path>: <string>}},
+      "structure_overrides":       {<zone_id>: {"slot_order": [<slot_key>, ...], "hidden_slots": [<slot_key>, ...]}}
     }
 
 ``image_id`` is the stable identifier emitted by the user-content image
@@ -58,13 +68,21 @@ from typing import Any, Optional
 _PKG_ROOT = Path(__file__).resolve().parent.parent
 DEFAULT_OVERRIDES_ROOT = _PKG_ROOT / "data" / "user_overrides"
 
-# The seven in-scope axes (IMP-51 #79 u1 added ``image_overrides``; IMP-45
+# The nine in-scope axes (IMP-51 #79 u1 added ``image_overrides``; IMP-45
 # #74 u1 added ``slide_css``; IMP-55 #93 u1 added
 # ``manual_section_assignment`` — bool intent marker that gates whether
-# persisted ``zone_sections`` are consumed by the backend pipeline). Any
-# other top-level key in the file is preserved but ignored by callers —
-# keeps the file forward-compatible with future axes (e.g., zone_sizes)
-# without a schema bump here.
+# persisted ``zone_sections`` are consumed by the backend pipeline; IMP-56
+# #90 u1 added ``text_overrides`` — Step-22 text-edit persist axis keyed by
+# ``{zone_id: {text_path: value}}`` where ``text_path`` is the
+# ``{slot_key}.{line_index}`` stamp emitted by u8 / consumed by u4+u5;
+# IMP-56 #90 u2 added ``structure_overrides`` — Step-22 structure-edit
+# persist axis keyed by ``{zone_id: {"slot_order": [...], "hidden_slots":
+# [...]}}``, scope LOCKED to slot reorder + hide so the resolver (u6) /
+# Step-12 apply (u7) cannot mutate frame identity — frame swap stays on
+# the existing ``frames`` axis to keep Phase Z's no-AI-HTML-structure
+# invariant intact). Any other top-level key in the file is preserved but
+# ignored by callers — keeps the file forward-compatible with future axes
+# (e.g., zone_sizes) without a schema bump here.
 KNOWN_AXES: tuple[str, ...] = (
     "layout",
     "zone_geometries",
@@ -73,6 +91,8 @@ KNOWN_AXES: tuple[str, ...] = (
     "image_overrides",
     "slide_css",
     "manual_section_assignment",
+    "text_overrides",
+    "structure_overrides",
 )
 
 # Key validation — MDX stem must be safe for filesystem use. Allow