[GEMINI] Document custom forensics metadata parser architectural decision

ARCHITECTURE.md

@@ -50,6 +50,7 @@ Houses the logic for generic CLI context and active competition commands:
 
 ### D. Forensics ([forensics.py](file:///home/venus/code/ctf/src/ctf/forensics.py))
 Implements specialized forensic inspection utilities registered as a nested subgroup under the CLI:
+*   **Custom Extractor**: Implements our own pure-Python, zero-dependency parser for standard TIFF/EXIF tags, Adobe XMP XML blocks, Photoshop IPTC IIM records, and JPEG/PNG physical parameters, rather than importing large external libraries.
 *   `info`: Inspects target file sizes, reads magic bytes, and warns if extensions do not match detected signatures.
 *   `flag-search`: Extracts printable string sequences (equivalent to GNU `strings`) and matches them against regular expression patterns to find potential flags.