When recovering missing tool results, the session recovery hook was using
raw part.id (prt_* format) as tool_use_id when callID was absent, causing
ZodError validation failures from the API.
Added isValidToolUseID() guard that only accepts toolu_* and call_* prefixed
IDs, and normalizeMessagePart() that returns null for parts without valid
callIDs. Both the SQLite fallback and stored-parts paths now filter out
invalid entries before constructing tool_result payloads.
Includes 4 regression tests covering both valid/invalid callID paths for
both SQLite and stored-parts backends.
YeonGyu-Kim