feat(context): add CPG-07 explicit sidecar composition gates

[Wibias]

Summary

• Stack CPG-07 on CPG-06.
• Make live recovery eligibility depend on actual sidecar plans, not coarse parser/config markers.
• Preserve the conservative rollout: active web-search, image, video, or vision sidecars suspend large-result recovery for that turn.
• Verify compaction, continuation, retry/failover boundaries and raw-reasoning replay without merging recovery semantics into the existing media/web loops.

Scope decision after deep review

The original CP-07 roadmap called this stage "stateless sidecar composition". This PR intentionally implements the safe composition boundary, not a merged recovery+sidecar execution loop. Full recovery composition with web/media/vision is deferred until CPG-08 has live-provider task-quality, cost-per-success and latency evidence for the simpler stateless recovery path.

This narrowing is deliberate: implementing recovery inside multiple existing sidecar loops before the base recovery path clears its rollout gate would increase hidden-trajectory and stale-action risk without evidence that the extra complexity is justified. Until that gate passes, an actual active sidecar remains authoritative and large recovery fails open for that turn.

Why

CPG-06 intentionally over-suspended sidecars. CPG-07 refines this using the repository's real wsPlan, imgPlan, vidPlan, and visionPlan so unavailable/disabled sidecars do not create unnecessary cache boundaries, while active sidecars still fail open to their existing behaviour.

TDD

The first commit is RED and defines deterministic actual-plan composition-boundary semantics.

Future gate

Only after CPG-08 live evidence passes should a later revision of this stage add provider-private sequences such as recovery -> web search, web search -> recovery, recovery -> media, sidecar failure after recovery, and mixed real-tool regeneration. If that evidence does not pass, this conservative boundary is the intended final behaviour.

Stack

• Base: agent/context-projection-cp06 / PR feat(context): add CPG-06 stateless recovery-priority loop #21
• Do not merge before its parent.

[github-actions]

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