Summary:
Add glyph detection post-conversion. If parsing leaves glyphs unresolved (meaning text appears as isolated character artifacts), these need to be detected and flagged similarly to how merged table cells are currently surfaced to the user.

Acceptance Criteria:

• Parse the final Docling document and check for glyph artifacts.

• Report glyphs clearly in the CLI summary output and JSON output.

• Treat glyph issues as critical issues that need user attention.

• Update README to describe glyph detection behavior.