test(context): pin CPG-09 stateful recovery deferral

[Wibias]

Summary

• Stack the CPG-09 readiness guard on CPG-08.
• Do not enable Cursor/Kiro provider-stateful recovery because CPG-08 has no live provider trials and therefore does not satisfy the plan's rollout gate.
• Distinguish transport shape from provider state: Cursor uses runTurn, while Kiro uses build/fetch/parse with provider-private continuation state.
• Declare provider statefulness explicitly through ProviderAdapter.contextProjectionProviderStateful instead of inferring recovery safety from adapter names or transport shape.
• Pin the stateful_adapter fail-open behaviour for both forms of provider state.
• Verify the current Cursor 330-tool / 120,000-byte budget and demonstrate that an unpinned __ocx_context_v1 can be pruned from a full catalogue.
• Preserve the requirement that future Cursor recovery must either pin/guarantee the recovery tool or post-budget verify it and fail open.

Deep-review hardening

Kiro and Cursor now declare contextProjectionProviderStateful: true in the adapter registry. The core recovery capability planner consumes that explicit property. Stateless adapters assert that the capability is absent. This separates provider-owned continuation semantics from the unrelated adapterNeedsForcedContinuation() persistence helper and prevents a future stateful adapter from silently becoming recovery-eligible merely because it does not use runTurn.

Focused provider-path/stateful-deferral/evaluation/review-hardening tests and the full TypeScript typecheck passed after the final rebase onto CPG-08.

Scope decision after deep review

This PR is the CPG-09 readiness/deferral gate, not the completed provider-stateful recovery milestone from the original roadmap. That is intentional, not an implementation shortcut.

Stateful recovery must remain disabled until CPG-08 has live evidence for the simpler stateless path, including comparison against OpenAI HTTP previous_response_id continuation and Responses WebSocket continuation. Byte reduction or synthetic exact-recovery checks are not sufficient evidence.

Preconditions for enabling Cursor/Kiro recovery later

All of the following must be true first:

• CPG-08 live gate passes with zero protocol violations and the declared quality/cost/latency thresholds;
• canonical restart after provider-private state loss is proven;
• provider reconnect/process restart and compaction boundaries are covered;
• stale request-local refs never cross an outer-turn/provider-state boundary;
• hidden recovery cannot cross provider/account failover;
• recovery-then-real-action regeneration remains mandatory;
• the final provider-visible recovery tool is unique and guaranteed to survive any provider tool budget;
• Cursor's 330-tool / 120,000-byte catalogue limit is handled by pinning/guarantee or post-budget verification, never assumption;
• Kiro remains classified by provider-private continuation state rather than by transport shape alone.

If those conditions do not pass, this deferral is the intended final CPG-09 behaviour.

Why this is a deferred stage

The implementation plan permits provider-stateful recovery only after the stateless path is proven with live provider evidence. The checked-in CPG-08 evaluation has zero live provider attempts, so enabling recovery for Cursor or Kiro would violate that rollout gate.

Stack

• Base: agent/context-projection-cp08 / PR feat(context): add CPG-08 evaluation harness and rollout gates #23
• Do not merge before its parent.

[github-actions]

✅ Deterministic PR hygiene checks passed.

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