feat(#88): IMP-88 u1~u7 Step 17 retry chain — layout_adjust + image_fit + frame_internal_fit_candidate executors + dispatcher + entry

Step 17 salvage dispatcher previously only ran the 3 actions in
_SALVAGE_FAIL_BY_ACTION (cross_zone_redistribute / glue_compression /
font_step_compression). Any next_proposed_action outside that set hit
salvage_terminal_action and dropped through, so visual_check aborted on
layout_adjust / image_fit / frame_internal_fit_candidate cascades.

u1 — router data surface (src/phase_z2_router.py)
  - ACTION_BY_CATEGORY: image_aspect_mismatch -> image_fit (new row),
    frame_capacity_mismatch -> frame_internal_fit_candidate (was
    frame_reselect).
  - ACTION_IMPLEMENTATION_STATUS: layout_adjust / image_fit /
    frame_internal_fit_candidate flipped MISSING -> IMPLEMENTED with
    inline IMP-88 rationale.

u2 — failure_router cascade surface (src/phase_z2_failure_router.py)
  - FAILURE_TYPE_DESCRIPTIONS + SALVAGE_FAILURE_TYPE_BY_ACTION extended
    with layout_adjust_insufficient / image_fit_insufficient /
    frame_internal_fit_insufficient producers.
  - NEXT_ACTION_BY_FAILURE + NEXT_ACTION_RATIONALE +
    NEXT_ACTION_IMPLEMENTATION_STATUS rows added; cascade chain becomes
    font_step_compression -> layout_adjust -> frame_internal_fit_candidate
    -> frame_reselect -> details_popup_escalation (#64 terminal).

u3~u5 — planners + apply helpers (src/phase_z2_retry.py)
  - plan_layout_adjust / apply_layout_adjust_layout_css with
    _layout_swap_priority across 8-preset LAYOUT_PRESETS (preset switch,
    no shared-margin shrink per Phase Z spacing direction).
  - plan_image_fit / apply_image_fit_css scoped to frame slot using
    existing classifier image_event payload (object-fit + max-w/h
    derivation).
  - plan_frame_internal_fit_candidate / apply_frame_internal_fit_candidate_css
    stays inside declared frame contract envelope; emits infeasible path
    when envelope is absent.

u6~u7 — pipeline wiring (src/phase_z2_pipeline.py)
  - _SALVAGE_FAIL_BY_ACTION extended; _attempt_salvage_chain gains
    layout_adjust distinct-render branch + frame_internal_fit_candidate
    CSS-overlay branch + loop cap.
  - _attempt_step17_image_fit_single_pass added for image_fit entry.
  - §11.7.1 / §11.7.2 entry triggers wired; Step 17/18/19 artifact
    refresh + note logging closes the salvage_terminal_action fall-through
    for the 3 IMP-88 actions.

Tests
  - New: test_router_actions_imp88.py (12),
    test_failure_router_imp88_cascade.py (12),
    test_phase_z2_retry_layout_adjust.py (10),
    test_phase_z2_retry_image_fit.py (13),
    test_phase_z2_retry_frame_internal_fit.py (13),
    test_phase_z2_pipeline_salvage_imp88.py (8),
    test_phase_z2_pipeline_step17_entry_imp88.py.
  - Regression-aligned: test_phase_z2_failure_router_cascade.py,
    test_phase_z2_step17_salvage_chain.py — pre-existing cascade +
    salvage-chain assertions updated to the IMPLEMENTED surface.

Out of scope (separate axes / issues)
  - details_popup_escalation terminal body (#64).
  - frame_reselect MISSING flip (different axis).
  - Step 14/16 detection refinement.
  - Stage 0 mdx_normalizer integration (locked 2026-05-08).
  - AI fallback activation.

Guardrails respected
  - Phase Z spacing direction: layout_adjust switches preset; no shared
    margin shrink.
  - AI isolation contract: planners + dispatcher are deterministic; zero
    AI calls in u1~u7.
  - No hardcoding: routing + cascade live in router/failure_router data
    rows, not inline conditionals.
  - IMP-46 (#62) cache carve-out: untouched.
  - 1 commit = 1 decision unit: u1~u7 grouped as a single IMP-88 unit.

Stage 4 verification: 7 IMP-88 test files + 2 modified regression files
PASS (Claude #12 + Codex #12 consensus YES). Full-suite sweep deferred to
a separate step.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/phase_z2_router.py

@@ -25,13 +25,27 @@ from typing import Optional
 # ─── §4 mapping table (spec PHASE-Z-FIT-CLASSIFIER-ROUTER-SPEC §4) ──
 
 # category → proposed_action (primary)
+# IMP-88 (#88) u1 (2026-05-24): two ACTION_BY_CATEGORY edits to align the
+# primary router surface with PHASE-Z-PIPELINE-OVERVIEW.md Step 16 + Step 17
+# spec (anchor PHASE-Z-PIPELINE-OVERVIEW.md:321):
+#   1. NEW row `image_aspect_mismatch → image_fit` — closes the unmapped
+#      classifier emission (phase_z2_classifier.py:434-447) that previously
+#      returned proposed_action=None and stalled visual_check on overflow
+#      runs carrying image_event payloads.
+#   2. REMAP `frame_capacity_mismatch → frame_internal_fit_candidate`
+#      (previously frame_reselect) — OVERVIEW.md Step 17 locks
+#      frame_internal_fit_candidate as the per-zone first-pass salvage
+#      *inside* the declared frame envelope; frame_reselect (V4 top-k
+#      alternate frame swap) stays available downstream via the
+#      failure_router cascade (rerender_still_fails → frame_reselect).
 ACTION_BY_CATEGORY: dict[str, str] = {
     "minor_overflow":              "zone_ratio_retry",
     "moderate_overflow":           "layout_adjust",
     "structural_minor_overflow":   "zone_ratio_retry",
     "structural_major_overflow":   "details_popup_escalation",
     "tabular_overflow":            "details_popup_escalation",
-    "frame_capacity_mismatch":     "frame_reselect",
+    "image_aspect_mismatch":       "image_fit",
+    "frame_capacity_mismatch":     "frame_internal_fit_candidate",
     "layout_zone_mismatch":        "layout_adjust",
     "hard_visual_fail":            "abort",
 }
@@ -48,8 +62,13 @@ ACTION_RATIONALE: dict[str, str] = {
         "1+ structural unit 완전 잘림 → 의미 손실, popup 으로 escalate",
     "tabular_overflow":
         "표는 행 단위로 잘리면 의미 손실 → popup escalate (또는 table-friendly frame reselect)",
+    "image_aspect_mismatch":
+        "image 자연 비율과 렌더 비율 mismatch → frame 내부 image fit (object-fit / "
+        "max-w/h) 로 envelope 안에서 비율 회복. 공통 image CSS 변경 X (frame-scoped).",
     "frame_capacity_mismatch":
-        "composition capacity_fit 가 이미 mismatch 신호 → V4 top-k 의 다른 frame 평가",
+        "composition capacity_fit 가 이미 mismatch 신호 → frame contract envelope "
+        "안 internal fit 변형 (density / line rhythm / row 배치) 우선. "
+        "frame swap 은 cascade 다음 단계 (rerender_still_fails → frame_reselect).",
     "layout_zone_mismatch":
         "frame root 자체 overflow → layout preset 변경 또는 zone 키움",
     "hard_visual_fail":
@@ -61,7 +80,21 @@ ACTION_RATIONALE: dict[str, str] = {
 # A2 단계에서 이 매핑이 *어디까지 자동 처리되고 어디서 막히는지* trace 확보용
 ACTION_IMPLEMENTATION_STATUS: dict[str, str] = {
     "zone_ratio_retry":          "IMPLEMENTED",  # A3 (2026-04-29) phase_z2_retry.plan_zone_ratio_retry + pipeline orchestration
-    "layout_adjust":             "MISSING",
+    # IMP-88 (#88) u1→u7 (2026-05-24): three Step 17 retry actions registered
+    # here. u1 added the data-surface rows (initial state MISSING). u3/u4/u5
+    # landed the deterministic planners in src/phase_z2_retry.py. u6 wired the
+    # salvage dispatcher (_attempt_salvage_chain), and u7 wired the Step 17
+    # entry runtime (_attempt_step17_image_fit_single_pass + §11.7.1/§11.7.2).
+    # Status flips MISSING→IMPLEMENTED land here on u7 completion — once the
+    # end-to-end path (planner + apply + dispatcher + entry) is wired the
+    # action is IMPLEMENTED on the deterministic surface. (Same convention as
+    # IMP-12 u7 cascade rows below: planner-surface availability + orchestrator
+    # wiring together constitute IMPLEMENTED; route_action's
+    # implementation_status field reflects surface availability, not whether a
+    # given pipeline run has invoked the action.)
+    "layout_adjust":             "IMPLEMENTED",  # u3 plan_layout_adjust + u6 dispatcher branch + u7 cascade entry
+    "image_fit":                 "IMPLEMENTED",  # u4 plan_image_fit + u7 _attempt_step17_image_fit_single_pass entry
+    "frame_internal_fit_candidate": "IMPLEMENTED",  # u5 plan_frame_internal_fit_candidate + u6 dispatcher branch + u7 cascade entry
     # IMP-35 (#64) u3 — MISSING → IMPLEMENTED on the primary router surface.
     # `plan_details_popup_escalation` (below) provides the deterministic stub
     # that downstream units consume: u4 binds the AI split-decision contract