expandConfluenceLink silently drops fetch errors

[calin-marian]

Problem

expandConfluenceLink in main.zig uses catch return for page fetch and format errors. When a linked Confluence page fails to load (network error, 404, etc.), the function returns silently with no output. Users have no way to know why a linked page wasn't expanded.

Fix

Changed catch return to catch |err| with a warning message printed to stderr, including the page ID and error:

Warning: failed to fetch Confluence page 12345: error.HttpError

References

Fixed in PR #8 (commit 9d86c3f).