feature: enchanced error messages

[trogulja]

Summary

Enriches error messages throughout the library to provide better debugging context when failures occur, especially for production issues.

Changes

• Network timeout errors - Track all network requests during setContent and report pending/failed requests on timeout
• Body PDF loading errors - Include document-page index, layout dimensions, and buffer size
• Section PDF loading errors - Include section type (header/footer/background), page number, and dimensions
• PDF embedding errors - Include element type, page number, and layout coordinates
• No document pages found - Include template diagnostic info (child elements, HTML preview)
• Version bump - 1.1.1 → 1.1.2
• CLAUDE.md - Added project guidance file

Example error output

Before:

Error: Timed out after waiting 30000ms

After:

Error: Timed out after waiting 30000ms | Network: 2 pending, 1 failed | Pending: https://example.com/font.ttf | Failed: https://example.com/image.png (net::ERR_CONNECTION_REFUSED)

Test plan

• All unit tests pass (165 tests)
• New tests added for network tracking error enrichment
• Visual test excluded (expected rendering differences)

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