fix(browser): include IndexedDB versions in storage fingerprints

Hash the observed database version with object-store definitions at the CDP boundary. Missing, invalid, or imprecise versions preserve store evidence with incomplete coverage and an explanation. Mark the revised projection so historical store-only hashes cannot create false changes or prove unchanged versions. Preserve comparable metadata and independent storage changes.

Remove the redundant storage comparability wrapper and use each fingerprint's parsed scope instead of interpreting its identity string.

Validation: producer-to-comparison regressions and a compiled CLI to stdio MCP comparison passed, including version-only changes, invalid versions, legacy projections, and complete database additions/removals. Static and docs checks passed. CDP responses were simulated; no real browser runtime was exercised.

docs/browser-observation.md

@@ -94,6 +94,14 @@ content. Actual JSON properties with those names remain content. Reference-only
 objects, unsupported values, and opaque cookie partition identities remain
 incomplete. Previously exported fingerprints are not recomputed; recapture both
 sides when comparing captures produced across this decoder change.
+IndexedDB schema fingerprints with `projection_version: 2` include the observed
+database version and object-store definitions. A missing, malformed, or imprecise
+version leaves the schema fingerprint incomplete while retaining observed store
+facts. Historical fingerprints without this marker covered object stores only:
+matching historical hashes cannot establish unchanged database versions, and a
+historical hash is not compared with a version-bearing hash. Recapture both
+sides for a complete IndexedDB version comparison; other proven storage changes
+remain reportable.
 
 Script comparison groups observations by reported URL and compares unordered
 content samples. Producer inventory keys include optional metadata, so a changed