Renderer: add a long-title wrapping fixture

[OthmaneBlial]

Goal

Add one approved synthetic fixture that proves a maximum-length editable title wraps without clipping.

Allowed files

• examples/fixtures/
• tests/test_generate_pptx.py
• generate_pptx.py only if the fixture exposes a defect
• docs/VIEWER_MATRIX.md
• docs/assets/ for a versioned viewer screenshot

Fixture

Use synthetic text within the public schema limit. Include no private deck content, remote asset, or unlicensed font.

Acceptance criteria

• The fixture validates against the current schema.
• Exported title remains native editable text.
• Shape bounds stay on the 16:9 canvas and the shared preflight reports no overflow.
• Record viewer name, version, OS, and result.
• Add a deterministic regression test and run make test.

Maintainer availability

Post the proposed title and viewer before implementation. A maintainer will confirm that it exercises a distinct wrapping boundary.

Out of scope

Changing the title limit, replacing text with an image, or claiming untested viewer parity.