docs: Add comprehensive critical bug report (Bugs.md)

[kael-developer]

Summary

Adds a Bugs.md file at the repository root documenting 13 bugs discovered across the doclite embedded document database codebase.

Changes

• Created Bugs.md — A comprehensive bug report covering all Go source files in doclite/, doclite.go, and sharedlib/docliteexport.go

Bug Severity Breakdown

Severity	Count
CRITICAL	3
HIGH	5
MEDIUM	3
LOW	2

Key Findings

1. Most urgent: sharedlib/docliteexport.go UpdateOneDoc silently deletes documents instead of updating them
2. Data corruption on reload: diskInitBtree calculates 0 children for last root when NumDocuments % MinKeys == 0
3. Runtime crash: indexOfNodes panics on empty nodes slice
4. Cursor bug: NextObject recursively calls Next() instead of NextObject(), losing the type parameter
5. Race condition: cutOverflowfile performs Seek outside the mutex

Verification

All 13 bug entries have been verified against the actual source code:

• File paths, function names, and line references confirmed
• Suggested fixes are syntactically correct Go code
• Priority ordering accounts for bug interdependencies