[Docs]: Add a current capability maturity matrix distinct from target design contracts

[Fangjj0621]

Is there an existing issue about this?

• I have checked the existing issues.

Describe the issue

As a developer evaluating Astra for a real deployment, I cannot reliably tell which capabilities are production-shaped today and which are target contracts that the implementation is still converging toward.

The README presents Durable Work, checkpoints/recovery, provider admission, Runner execution, MCP, sandboxing, replay, Trace/Explain/Reflect, and learning as one coherent runtime. At the same time, many documents under docs/design/ explicitly say target design contract or target architecture baseline, and some of them contain migration roadmaps or required evolution areas.

This makes an architecture review unnecessarily risky: the documentation is individually detailed, but there is no single implementation-status view that answers:

• implemented and covered by default CI;
• implemented behind a feature flag or only for one runtime profile;
• implemented but requiring live MatrixOne/Memoria/provider infrastructure;
• partial or experimental;
• target design only;
• known-broken with an open issue.

The result is that a reader can easily mistake a normative contract for a currently supported product guarantee.

Suggested improvement

Add a versioned capability maturity matrix linked prominently from the README and documentation index. For each public capability, include:

Field	Example
Capability	Crash recovery, MCP tools, sandbox isolation, replay
Status	Stable / Beta / Experimental / Partial / Design-only
Supported profiles	CLI + Server / Server-only / Server + Edge
Default-enabled	Yes / No
Required dependencies	MatrixOne, Memoria, external model, Edge
Verification	Unit / offline integration / Matrix E2E / live provider
Known limitations	Link to issue or design gap
Compatibility	Since version and public contract stability

The matrix should be checked in CI so that new user-facing claims or public routes cannot be added without an explicit maturity status.

Acceptance criteria

• README links to one canonical current-capability matrix.
• Every core runtime claim has a current status and supported-profile list.
• Target-only contracts are visibly distinguished from shipped behavior.
• Known gaps link to their tracking issues.
• Releases snapshot the matrix so users can evaluate a specific version rather than main.

Additional information

Related documents:

• README.md
• docs/design/ARCHITECTURE.md
• docs/design/runtime-lifecycle.md
• docs/design/capability-system.md
• docs/testing/coverage-matrix.md