docs: align Runcap product truth and current scope

[kirder24-code]

Summary

• Adds docs/current-product-status.md with the current Runcap public boundary: coding spend control, mission scope, and Proof Gate merge eligibility.
• Rewrites the README opening so the public position is clear in under 20 seconds.
• Corrects quickstart naming/storage paths from old prototype names to current Runcap .runcap paths.
• Marks older roadmap/business/launch/product planning docs as historical.

GitHub About

Updated repository description to:

Local-first control layer for AI coding agents. Cap routed spend, constrain mission scope, and require CI replay before an AI-generated PR earns merge eligibility.

Validation

• npm run check
• npm test
• npm run test:tier3
• git diff --check
• git status -sb

Scope

Docs and public repository metadata only. No source code, package files, workflows, releases, tags, Marketplace settings, demo PRs, video assets, or dashboard stash were touched.