Add external metadata evidence ingestion

docs/module-internals.md

@@ -136,6 +136,8 @@ metadata extraction from verdict logic:
 
 - `extract_provenance_evidence` reads the supported metadata signals into
   `ProvenanceEvidence`.
+- `evidence_from_metadata_record` normalizes an externally collected nested
+  metadata record into the same evidence type without file access.
 - `identify_from_evidence` evaluates that evidence without reopening the source.
 - `identify` preserves the path-based API and adds the optional registered
   visible-mark and open invisible-watermark decoders after extraction.

docs/python-api.md

@@ -113,6 +113,28 @@ evidence = extract_provenance_evidence(Path("input.png"))
 report = identify_from_evidence(evidence)
 ```
 
+If metadata was collected by another component, normalize its nested record
+without reopening the original file:
+
+```python
+from remove_ai_watermarks.identify import (
+    evidence_from_metadata_record,
+    identify_from_evidence,
+)
+
+record = {
+    "pil": {"info:parameters": "Steps: 20, Sampler: Euler"},
+    "exif": {"0th": {"Software": "Stable Diffusion"}},
+}
+evidence = evidence_from_metadata_record(record, path=Path("input.png"))
+report = identify_from_evidence(evidence)
+```
+
+The normalizer recursively preserves text and byte values. It also decodes
+strings prefixed with `hex:` and fields named `base64` or ending in
+`_base64`. Pass a C2PA manifest-store dictionary in `record["c2pa_store"]`, or
+through the explicit `c2pa_manifest_store` argument.
+
 `identify_from_evidence` does not reopen the source file. It evaluates metadata
 only; registered visible marks and pixel-backed invisible watermarks remain in
 the path-based `identify` call.

docs/watermarking-landscape.md

@@ -33,7 +33,7 @@ Grok JPEG downloads (Aurora model) carry **no C2PA, no XMP, no SynthID, no IPTC*
 **Stripped on removal too:** `remove_ai_metadata` calls `_scrub_ai_exif` on
 JPEG EXIF, which deletes the xAI Signature and UUID Artist pair plus supported
 AI generator values while retaining unrelated camera and editor EXIF. The
-shared `_is_xai_signature_pair` helper is the single source of truth for the
+shared `xai_signature_pair` helper is the single source of truth for the
 pair. On the ISOBMFF path, `blank_ai_exif_tokens` provides the corresponding
 in-place scrub for supported EXIF values, TC260 AIGC blocks, and the xAI pair.
 - **China TC260 AIGC label (caught by `AIGC_MARKERS` / `metadata.aigc_label`, surfaced by `identify` as the `aigc` signal):** China-served generators embed an XMP `<TC260:AIGC>{"Label":"1","ContentProducer":...}` block — China's mandatory AI-content labeling (TC260 namespace `tc260.org.cn/ns/AIGC`).