Close #16: stop source_labels=False from delegating to wrong archetype formatter

[prekabreki]

What changed

Removed the two early-exit delegations in _format_document_archive and _format_mixed_media that re-routed source_labels=False to wrong archetype formatters. Now both functions always use their own classification paths and only suppress SOURCE_LABEL_OPEN/SOURCE_LABEL_CLOSE blocks when the toggle is off.

Files

• vo_format/formatter.py - Removed delegating return _format_single_narrator(...) at L803-804 and return _format_multi_voice_drama(...) at L1076-1077; guarded all SOURCE_LABEL_OPEN/SOURCE_LABEL_CLOSE appends with if toggles.source_labels:
• tests/test_formatter.py - Added two regression tests asserting (block_type, text) sequence equality between on-run (labels stripped) and off-run for both document_archive_sample.md and mixed_media_sample.md

Assumptions made

• in_source_block tracking is preserved for indentation purposes even when labels are suppressed
• RE_DOC_REF matching and document_section/narrative_label handling proceed unchanged - only the label container blocks are conditional

Uncertainties

None

Test

./.venv/Scripts/python.exe -m pytest tests/ -q - 461 passed, 2 skipped