test(thinking-recovery): add unit tests for all exported functions

Cover analyzeConversationState, needsThinkingRecovery, closeToolLoopForThinking,
looksLikeCompactedThinkingTurn, and hasPossibleCompactedThinking.

Tests verify: empty/null guards, tool-loop detection, turn-start tracking,
thinking-strip on recovery, synthetic message content (singular/plural/fallback),
and compacted-turn heuristic boundary cases.