feat(#64): IMP-35 details_popup_escalation u1~u10 + Stage 3 R7 anchor re-pin

Land the production + test surface for the Step 17 cascade POPUP terminal
(DETERMINISTIC -> POPUP -> AI_REPAIR -> USER_OVERRIDE) per Stage 2 plan R2.
u11 (baseline-red invariance gate) was already landed in 7c93031 ahead of
this commit; this commit completes u1~u10 plus the Stage 3 R7 follow-up
anchor re-pin for test_imp17_comment_anchor.py.

Implementation units (Stage 2 R2 contract):
  u1  frame_reselect_insufficient failure_type + post-frame remeasure (q4)
        - src/phase_z2_failure_router.py, src/phase_z2_pipeline.py
  u2  NEXT_ACTION_BY_FAILURE row + impl_status flip
        - src/phase_z2_failure_router.py
  u3  Router details_popup_escalation MISSING->IMPLEMENTED + executor stub
        - src/phase_z2_router.py
  u4  step17.py AI split-decision contract (POPUP cascade_stage +
      route_for_label + skip_reason); API gated
        - src/phase_z2_ai_fallback/step17.py
  u5  Step 17 POPUP gate executor; popup_escalation_plan + has_popup marker
        - src/phase_z2_pipeline.py, src/phase_z2_ai_fallback/step17.py
  u6  Composition popup binding -- yaml strategy -> zone payload
        - src/phase_z2_composition.py
  u7  Pipeline composer -> render_slide wiring
      (popup_html / preview_text / has_popup)
        - src/phase_z2_pipeline.py
  u8  slide_base.html <details>/<summary> popup wrapper
        - templates/phase_z2/slide_base.html
  u9  display_strategies.yaml inline_preview + popup metadata
        - templates/phase_z2/regions/display_strategies.yaml
  u10 MDX preservation invariant: popup=full source / body=summary or subset
        (asserted by tests/phase_z2/test_popup_mdx_preservation.py)
  u11 (already in 7c93031) -- baseline-red invariance gate

Stage 3 R7 follow-up (anchor re-pin, test-only):
  - tests/orchestrator_unit/test_imp17_comment_anchor.py
    Pre-anchor additions in src/phase_z2_pipeline.py (u1 / u5 / u7) shifted
    the restructure/reject route-hint comments 578/579 -> 586/587. Re-pinned
    the two guard tests (and docstring re-pin lineage 564 -> 570 -> 578 ->
    586). Production code untouched.

Verification (Stage 4 R1):
  pytest -q tests/orchestrator_unit/test_imp17_comment_anchor.py
    -> 2 passed / 0.02s
  pytest -q <10 IMP-35 unit files in tests/phase_z2 + tests/phase_z2_ai_fallback>
    -> 136 passed / 15.94s
  Baseline-red invariance gate
    (tests/test_imp47b_step12_ai_wiring.py +
     tests/test_phase_z2_ai_fallback_config.py)
    -> 4 failed / 6 passed; FAILED set === IMP35_BASELINE_RED_NODE_IDS
    (frozen registry from 7c93031). Contract holds.
  Codex Stage 4 R1 = YES (independent verify).

Guardrails honored:
  - MDX content preservation: popup carries full source, body holds
    summary or subset only (CLAUDE.md 자세히보기 원칙;
    feedback_phase_z_spacing_direction -- capacity expanded, no margin shrink).
  - AI isolation contract: Step 17 POPUP gate is deterministic; AI hook
    surface is split-decision contract only, API call gated.
  - No hardcoding: escalation thresholds derived from existing overflow
    detector outputs; preview_chars deterministic from container px.
  - 1 commit = 1 decision unit: u1~u10 land together as the planned
    production surface; u11 was deliberately split into 7c93031 as Stage 3
    R7 carve-out, and the R7 anchor re-pin rides with this commit because
    it is the direct shift consequence of the u1/u5/u7 pre-anchor additions.
  - Scope-locked: .claude/settings.json explicitly excluded
    (Stage 4 exit report contract).

Out of scope (per Stage 1 + Stage 2):
  - AI_REPAIR API activation (post IMP-35 axis).
  - IMP-34 zone resize, IMP-36 responsive fit (chain partners,
    separate issues).
  - Print-time auto-expand JavaScript for <details>.
  - Popup escalation in stages other than Step 17.
  - Baseline-red body repair (4 frozen failures) -- separate follow-up
    issue; u11 only guards the count.
  - frame_reselect algorithm changes (entry point only).
  - templates/phase_z2/slide_base.html path rename.

source_comment_ids:
  Stage 1: claude_stage1_problem_review_imp35, codex_stage1_verification_imp35_yes
  Stage 2: Claude #4 R2 plan, Codex #5 R2 YES
  Stage 3: Claude #86 (R7 anchor re-pin), Codex #87 YES
  Stage 4: Claude #88 R1, Codex #89 R1 YES

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

tests/orchestrator_unit/test_imp17_comment_anchor.py

@@ -17,6 +17,13 @@ shifted only the post-comment table downward. The restructure anchor itself move
 the restructure line. Re-pinned 570 → 578 (restructure / IMP-17) and 571 → 579
 (reject / IMP-47B supersession of the prior IMP-29 reference).
 
+Anchor re-pin (2026-05-23, IMP-35 u1/u5/u7 / Gitea #64 Stage 3): IMP-35 added a
+single-line ``compose_zone_popup_payload`` import (u7) plus a 7-line
+``run_step17_popup_gate`` import block (u5) ahead of the route-hint table, totaling
++8 lines of pre-anchor additions. The post-import body shifted uniformly downward;
+the restructure anchor moved 578 → 586 and the reject anchor moved 579 → 587.
+Re-pinned 578 → 586 (restructure / IMP-17) and 579 → 587 (reject / IMP-47B).
+
 Run: pytest -q tests/orchestrator_unit/test_imp17_comment_anchor.py
 """
 from pathlib import Path
@@ -29,17 +36,17 @@ def _lines() -> list[str]:
     return PIPELINE.read_text(encoding="utf-8").splitlines()
 
 
-def test_line_578_references_imp17_not_imp31():
-    line = _lines()[577]  # 1-indexed line 578
-    assert "restructure" in line, f"line 578 anchor drifted: {line!r}"
-    assert "IMP-17" in line, f"line 578 must reference IMP-17 (carve-out): {line!r}"
-    assert "IMP-31" not in line, f"line 578 must not reference non-existent IMP-31: {line!r}"
+def test_line_586_references_imp17_not_imp31():
+    line = _lines()[585]  # 1-indexed line 586
+    assert "restructure" in line, f"line 586 anchor drifted: {line!r}"
+    assert "IMP-17" in line, f"line 586 must reference IMP-17 (carve-out): {line!r}"
+    assert "IMP-31" not in line, f"line 586 must not reference non-existent IMP-31: {line!r}"
 
 
-def test_line_579_references_imp47b_supersession():
-    line = _lines()[578]  # 1-indexed line 579
-    assert "reject" in line, f"line 579 anchor drifted: {line!r}"
+def test_line_587_references_imp47b_supersession():
+    line = _lines()[586]  # 1-indexed line 587
+    assert "reject" in line, f"line 587 anchor drifted: {line!r}"
     assert "IMP-47B" in line, (
-        f"line 579 must reference IMP-47B (supersedes prior IMP-29 reject disposition): "
+        f"line 587 must reference IMP-47B (supersedes prior IMP-29 reject disposition): "
         f"{line!r}"
     )