feat: WP-0003 complete — LEVEL3 advanced features + error framework

Implements full LEVEL3 feature set: cross-references (xref.py), numbered
figures (figures.py), auto-diagrams (diagrams.py), bibliography/citations
(bibliography.py), LEVEL3 capability detection (level3.py), and structured
error/warning records (errors.py). Builder, importer, and differ updated for
LEVEL3 round-trip support. REST and MCP interfaces updated with structured
warning records. 259 tests passing.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/markidocx/differ.py

@@ -5,6 +5,8 @@ from __future__ import annotations
 import re
 from dataclasses import dataclass, field
 
+from markidocx.errors import OutputState
+
 HEADING_RE = re.compile(r"^(#{1,6})\s+(.+)$", re.MULTILINE)
 LIST_ITEM_RE = re.compile(r"^(\s*[-*+]|\s*\d+\.)\s+(.+)$", re.MULTILINE)
 TABLE_ROW_RE = re.compile(r"^\|.+\|$", re.MULTILINE)
@@ -19,6 +21,7 @@ class DriftReport:
     degraded: list[str] = field(default_factory=list)
     broken: list[str] = field(default_factory=list)
     unsupported: list[str] = field(default_factory=list)
+    output_state: OutputState = OutputState.FINAL
 
 
 def compare(original: str, reimported: str) -> DriftReport:
@@ -76,13 +79,29 @@ def compare(original: str, reimported: str) -> DriftReport:
         else:
             degraded.append(f"link:lost {link[:40]}")
 
+    # --- Cross-references (FR-531, FR-540) ---
+    _compare_xrefs(original, reimported, preserved, degraded, broken)
+
+    # --- Figures (FR-532, FR-541) ---
+    _compare_figures(original, reimported, preserved, degraded, broken)
+
+    # --- Citations & Bibliography (FR-535, FR-542) ---
+    from markidocx.bibliography import compare_citations
+
+    compare_citations(original, reimported, preserved, degraded, broken)
+
     has_drift = bool(degraded or broken)
+    output_state = (
+        OutputState.FINAL if not has_drift
+        else (OutputState.DEGRADED if not broken else OutputState.PARTIAL)
+    )
     return DriftReport(
         has_drift=has_drift,
         preserved=preserved,
         degraded=degraded,
         broken=broken,
         unsupported=unsupported,
+        output_state=output_state,
     )
 
 
@@ -104,6 +123,64 @@ def _count_tables(text: str) -> int:
     return count
 
 
+def _compare_figures(
+    original: str,
+    reimported: str,
+    preserved: list[str],
+    degraded: list[str],
+    broken: list[str],
+) -> None:
+    """Compare figure labels and captions (FR-532, FR-541)."""
+    from markidocx.figures import extract_figure_captions, extract_figure_labels
+
+    orig_labels = extract_figure_labels(original)
+    reim_labels = extract_figure_labels(reimported)
+    for label in orig_labels:
+        if label in reim_labels:
+            preserved.append(f"figure-label:{label}")
+        else:
+            broken.append(f"figure-label:missing '{label}'")
+
+    orig_captions = extract_figure_captions(original)
+    reim_captions = extract_figure_captions(reimported)
+    orig_set = set(orig_captions)
+    reim_set = set(reim_captions)
+    for caption in orig_set:
+        if caption in reim_set:
+            preserved.append(f"figure-caption:{caption[:40]}")
+        else:
+            degraded.append(f"figure-caption:lost '{caption[:40]}'")
+
+
+def _compare_xrefs(
+    original: str,
+    reimported: str,
+    preserved: list[str],
+    degraded: list[str],
+    broken: list[str],
+) -> None:
+    """Compare cross-reference anchors and links (FR-531, FR-540)."""
+    from markidocx.xref import extract_anchors, extract_xref_links
+
+    orig_anchors = extract_anchors(original)
+    reim_anchors = extract_anchors(reimported)
+    for anchor in orig_anchors:
+        if anchor in reim_anchors:
+            preserved.append(f"xref-anchor:{anchor}")
+        else:
+            broken.append(f"xref-anchor:missing '{anchor}'")
+
+    orig_xrefs = extract_xref_links(original)
+    reim_xrefs = extract_xref_links(reimported)
+    for link_text, anchor in orig_xrefs:
+        if (link_text, anchor) in reim_xrefs:
+            preserved.append(f"xref-link:[{link_text}][{anchor}]")
+        elif anchor not in reim_anchors:
+            broken.append(f"xref-link:broken-target [{link_text}][{anchor}]")
+        else:
+            degraded.append(f"xref-link:degraded [{link_text}][{anchor}]")
+
+
 def _compare_sets(
     kind: str,
     orig: list[str],