feat(IMP-17): AI repair fallback infra carve-out — design-only boundary + 3-cond AND gate

u1 — src/phase_z2_pipeline.py:564 route hint comment corrected from
non-existent IMP-31 to IMP-17 (carve-out, AI fallback only, normal path 밖).
Line 565 IMP-29 frontend override reference untouched.

u2 — docs/architecture/IMP-17-CARVE-OUT.md (new) defines:
- allowed scope (Step 12 restructure proposal, Step 16/17 retry fallback)
- forbidden scope (normal-path AI calls, MDX compression, HTML structure)
- 3-condition AND activation gate (User GO ∧ B4 frame_selection evidence
  ∧ IMP-04 catalog + IMP-05 V4 fallback live)
- pattern shape reference (link-only): content_editor.py:21,318 +
  sse_utils.py:16-50 (Phase Q Archive Candidate, no port)
- AI 격리 contract + Kei persona 단절 (permanent)

u3 — PHASE-Z-IMPLEMENTATION-ISSUE-BACKLOG.md:68 IMP-17 row gains
carve-out doc link + 3-cond AND gate pointer.

u4 — PHASE-Q-INSIGHT-TO-22STEP-MAP.md AI repair fallback infra registry
row prefixed with IMP-17 + carve-out link; normal_path=no preserved.

Anchor test: tests/orchestrator_unit/test_imp17_comment_anchor.py asserts
line 564 IMP-17 wording AND line 565 IMP-29 preservation (2 tests pass).

Runtime behavior change: 0. Only delta in executable file is one comment
line. Normal-path AI invocation count remains 0.

Refs: gitea #17

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

src/phase_z2_pipeline.py

@@ -561,7 +561,7 @@ def lookup_v4_match(
 # (frontend zone-level override / AI-assisted adaptation). Codex #2 conceptual model :
 #   use_as_is    → Phase Z direct render
 #   light_edit   → deterministic minor adjustment
-#   restructure  → AI-assisted frame-aware adaptation (deferred to IMP-31)
+#   restructure  → AI-assisted frame-aware adaptation (deferred to IMP-17 — carve-out, AI fallback only, normal path 밖)
 #   reject       → design reference only (deferred to IMP-29 frontend override)
 _IMP05_ROUTE_HINTS: dict[str, str] = {
     "use_as_is":   "direct_render",