docs: add financial-grade roadmap and persistence architecture

[blove]

Summary

• establish a canonical Now / Next / Later roadmap for financial-grade portfolio-management and financial-planning grids
• define the persistence and history sequence: saved views, bounded command undo/redo, revisioned mutations, then durable audit/version history
• document authority and lifecycle rules, preserve historical planning records with clear notices, and link the roadmap from the root README
• specify financial-grade mutation safety, including atomic command-ID reservation, exactly-once provider execution, conflict/resync behavior, and capability-gated reverts

Why

The repository had strong dated designs, plans, changelogs, API reports, and benchmark evidence, but no durable current roadmap or clear authority rules. Existing runtime state, editing, paste, and transaction primitives also needed an explicit architectural boundary before persistence and history APIs are designed.

Validation

• Prettier check for all seven changed Markdown files
• whitespace checks for the committed and working-tree diffs
• required repository-relative link-target checks
• documentation-only seven-file scope check
• pnpm test — 1,900 tests passed

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Project	Deployment	Actions	Updated (UTC)
pretable	Ready	Preview	Aug 10, 2026 3:35pm

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