fix(nwsync): close the review findings on the framing fix and verify

- compressBlob now asserts its own output declares a content size, instead of
  trusting that the only way to lose the field is the one #86 found. An encoder
  upgrade that finds another way would otherwise republish the same undecodable
  blob in silence, and a blob is skipped by every later emit once written.
- inspectBlob asserts the frame whenever one is present, rather than only when
  the payload is non-empty.
- dirSink stats instead of reading when not verifying. Reading every existing
  blob back on the default path was a plain regression, and it contradicted the
  documented promise that verifying is a repair pass, not the default.
- The manifest sha1 is now checked as hex before it is interpolated into a URL
  path, rather than only measured.
- One blobKey rule for where a blob lives, replacing three copies of the
  fanout-path expression.
- Renamed frameSizeThreshold to oneByteContentSizeCeiling, which says whose
  threshold it is.
- The read-back in zoneSink reads the storage API on purpose; said so, and
  corrected a comment that claimed a failed read-back re-uploads when it
  aborts.
- Tests derive their expected blob counts from the run instead of hard-coding
  fixture arithmetic, and the size-mismatch category has a test.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

README.md

@@ -19,7 +19,7 @@ Crucible is how the artifact repos turn source into artifacts.
 | `crucible-depot`   | `crucible depot`   | content-addressed depot blob verify/move        |
 | `crucible-hak`     | `crucible hak`     | ERF/HAK pack/unpack + hak manifests             |
 | `crucible-module`  | `crucible module`  | build/extract/validate/compare the `.mod`       |
-| `crucible-nwsync`  | `crucible nwsync`  | NWSync blob emit + manifest assemble            |
+| `crucible-nwsync`  | `crucible nwsync`  | NWSync blob emit + manifest assemble + verify   |
 | `crucible-topdata` | `crucible topdata` | compile 2da/tlk topdata + packages              |
 | `crucible-wiki`    | `crucible wiki`    | render + deploy mechanical wiki pages           |