Define first default chart structure preset

Problem

Investigate and define the first default chart structure preset for M1, including axis side posture, guide and grid philosophy, legend placement, title anchoring, padding, and whether to refine editorial or introduce a dedicated structure file.

Context

• The M1 chart-batch task still has an unresolved structural question: whether the current editorial structure is close enough to serve as the first real default, or whether M1 needs a dedicated structure preset.
• This is broader than any one axis or grid decision. It includes the first coherent answer for scaffold posture across the required chart families: axis side, grid/domain visibility, title anchor, padding, legend placement, and default spacing behavior.
• The main implementation seams are:
• dataface/core/compile/chart_structures/*.yml
• dataface/core/compile/default_config.yml
• dataface/core/render/chart/presentation.py
• dataface/core/render/chart/standard_renderer.py
• This task should absorb and organize several open M1 structural questions that are currently scattered through m1-pilot-chart-batch.md.
• Constraint: keep the structure layer about scaffold and posture, not paint. Palette and neutral-token work now have separate M1 tasks.

Possible Solutions

• Keep editorial as the default with only minimal patching. Trade-offs: fastest path, but risks carrying accidental prototype posture into the first real default experience.
• Recommended: explicitly audit editorial against M1 needs, then either refine it deliberately or fork a dedicated first-default structure preset with a small, documented set of scaffold rules. Trade-offs: more work now, but it makes the first structure intentional and easier to evolve.
• Add many chart-family-specific structure presets immediately. Trade-offs: expressive, but too broad before the first default structure is proven.

Plan

1. Inventory the structural rules the M1 batch actually needs to feel coherent.
2. Compare those needs against the current editorial preset and renderer heuristics.
3. Decide whether to refine editorial or create a new first-default preset.
4. Record the chosen property set and file ownership.
5. Break implementation follow-ons into scoped tasks only where needed.

Implementation Progress

• 2026-03-25: Task created to pull the open structure-default question out of the overloaded M1 pilot batch task and give it a dedicated home.

QA Exploration

• [ ] QA exploration completed (or N/A for non-UI tasks)

Review Feedback

• [ ] Review cleared