fix(sqlite): preserve snapshot admission failure semantics

Refuse oversized database and WAL inputs before acquisition with exact observed bytes and export guidance. Keep initial path failures separate from file-set changes and retain cleanup and partial observations on late growth.

Refs #4208, #4188, #4141, #4127

Co-authored-by: hima <1ep23ic023@eastpoint.ac.in>
Co-authored-by: Royce <roycelam@umich.edu>

docs/sqlite-databases.md

@@ -105,6 +105,20 @@ overall native heap and total resident memory are not capped. Row limits do not
 override these byte and resource limits. Resource-limit failures do not return
 an incomplete schema as successful complete evidence.
 
+If the combined database and WAL exceed the snapshot budget, the refusal is a
+`resource_constraint` and reports both the configured byte limit and the exact
+observed combined size as a decimal string. The remediation directs callers to
+create a smaller consistent offline snapshot containing only relevant data
+through the application's supported export workflow. A generic backup or copy
+does not guarantee a smaller result; REA does not truncate or modify the
+selected source.
+
+On hosts that cannot address the derived WAL or rollback-journal path for a
+long selected database name, REA reports that the SQLite capability is
+unavailable. It does not assume an inaccessible sidecar is absent. Use the
+application's supported consistent offline export or copy workflow to place
+the complete known file set at a shorter path.
+
 MCP also applies its configured response budget to the complete Evidence
 envelope. If delivery exceeds that budget, it reports a transport constraint
 with guidance for exporting retained Evidence, requesting a matching larger