fix(elf): distinguish compressed note storage from decoded notes

Refuse compressed note sections with typed unsupported-target semantics before framing or decoding, preserving stored-range checks and physical descriptor-offset provenance. Flutter retains independent build IDs with partial coverage when compressed notes are skipped. Verify the existing shared alignment fix with prefixed notes across classes and table kinds.

Fixes #6869
Closes #6563

docs/elf-notes.md

@@ -58,5 +58,13 @@ numbering (`PN_XNUM`, including a section count stored when `e_shnum` is 0) is
 unsupported and returns an unsupported-target outcome rather than invalid-input
 recovery.
 
+`SHF_COMPRESSED` note sections return `unsupported_target` before their payload
+is interpreted or decompressed. Their compression header is storage metadata,
+not a note header. The current result requires physical file offsets for each
+note and descriptor, which decoded compressed notes cannot provide. This refusal
+does not label compressed note storage as malformed or allocate its declared
+decoded size. Compressed section-name tables remain supported within the limits
+above.
+
 This workflow does not execute the image or verify GNU build-id uniqueness
 against package catalogs.