docs: plan beta10 to alpha roadmap

[brik64-admin]

Summary

• Adds a Beta10-to-alpha roadmap document for the public CLI lane.
• Tracks telemetry, feedback, automatic error reporting, SDK/skills alignment, source-lift preview, local/cloud split, alpha hardening, and the separate L6+N5 fixpoint lane.
• Links roadmap issues [Roadmap] Beta10 modular PCD, diagnostics and SDK ESM #90-[Carril B] L6+N5 self-host/fixpoint milestone remains separate #97 from the document.

Claim boundary

• Documentation-only change.
• Does not implement telemetry, feedback, error reporting, compiler features, or L6+N5 fixpoint.
• Keeps Carril A product releases separate from Carril B claim-bearing self-host/fixpoint work.

Verification

• git diff --check
• GitHub issues [Roadmap] Beta10 modular PCD, diagnostics and SDK ESM #90-[Carril B] L6+N5 self-host/fixpoint milestone remains separate #97 created and linked