fix(apple): preserve empty IPS text and source keys

Keep observed empty JSON strings separate from missing fields in IPS process,
image, frame, register and OS-version facts. Preserve empty unlisted keys,
retain malformed UUID source text, and keep unknown architecture interpretation
separate from raw spelling. Classification excludes empty supporting fields.

Validate producer cases plus compiled CLI and stdio MCP delivery against the
same output contract. This is saved-report inspection, without target execution.

docs/apple-ips.md

@@ -38,9 +38,16 @@ address uses that row's own image base and offset. The recorded `inline` flag
 does not supply a missing offset or authorize borrowing another row's address.
 When `faultingThread` is missing or does not resolve to a recorded thread
 object, row-zero roles are `unknown`; the recorded lookup remains available.
+Observed JSON strings retain `""`; `null` means the field was missing or JSON
+`null`. This includes image paths, frame symbols, process text, and the older
+string `osVersion` form. Unlisted JSON keys and generic register names also
+retain empty spellings. An empty image architecture remains recorded as `""`
+while `uuid_unknown` stays true, since that spelling does not establish an
+architecture. An empty UUID is malformed, so its exact spelling appears in
+`coverage.type_mismatches` and its canonical UUID remains unknown.
 `process.os_version` keeps the producer's dictionary (`train`, `build`,
 `release_type`, `is_embedded`) or the older string form. Image UUIDs are uppercase 8-4-4-4-12; an all-zero UUID
-or a missing `arch` is `uuid_unknown`. Image `source` letters keep their
+or a missing or empty `arch` is `uuid_unknown`. Image `source` letters keep their
 documented meaning (`P` process, `S` shared cache, `C` shared cache library,
 `K` kernel, `U` kernel cache, `T` kernel text exec, `A` absolute). Keys the
 documentation does not list remain in `unlisted_keys` or `unlisted_body_keys`.