Normalize standard Skin V1 surface shell continuity

[BryanHarrisScripts]

Refs #2030.

Human review of the 12 WebMCP candidates found a small but visible shell inconsistency: subordinate surfaces use different outer widths and return/header treatments even though the content itself is accepted.

This pass is deliberately CSS-only:

• keeps Dashboard unique as the canonical landing composition;
• normalizes Community, Identity, General, Local Story Mode, Cloud Story Mode, Node Info, Agents, Bug Report and Notices to the canonical Skin V1 shell width;
• gives their return-action strip one consistent solid Skin V1 treatment;
• removes General's alternate stepped header fill so it matches the established subordinate title treatment;
• does not change content, navigation, provider behavior, settings behavior or the 12-surface WebMCP registry;
• keeps Manage and Writer's Craft on their existing canonical shell geometry.

#2030 was reopened because Human visual approval/locking was still outstanding. Merge only when exact-head Architecture Verification is green; then rerun local WebMCP, visually approve the refreshed 12 candidates, lock approved baselines, and close #2030.