submit_pull_request_review max > 1 collapses batch to first target and last body

[ianreay]

Problem

submit_pull_request_review accepts max > 1, and scheduled workflows with target: "*" can emit multiple calls with different pull_request_number values. The runtime accepts every call but finalizes only one review:

• target/review context comes from the first call;
• body/event metadata comes from the last call;
• intermediate calls are silently lost;
• the workflow can still conclude successfully.

Source-level cause

This behavior is present in v0.80.9 through at least v0.82.7:

• safe_output_handler_manager.cjs creates one shared createReviewBuffer() for the entire run and calls submitReview() once.
• submit_pr_review.cjs routes every accepted message into that shared buffer.
• pr_review_buffer.cjs#setReviewContext only sets context when it is null (first target wins).
• pr_review_buffer.cjs#setReviewMetadata overwrites existing metadata and documents "last call wins."
• finalization performs one pulls.createReview().

The advertised max therefore permits a cardinality the handler cannot preserve.

Live reproduction

Volaris-AI/project-template Software Architect run:
https://github.com/Volaris-AI/project-template/actions/runs/28719559657

The v0.80.9 artifact contains five correctly paired safe-output calls for PRs #4099, #4096, #4094, #4103, and #4106. GitHub received exactly one review: on first target #4099, containing the fifth body intended for #4106:
https://github.com/Volaris-AI/project-template/pull/4099#pullrequestreview-4630267575

A v0.81.6 run reproduces the same first-target/last-body pairing:
https://github.com/Volaris-AI/project-template/actions/runs/29135313394

Expected behavior

Each accepted message must remain paired with its repository, PR, body, event, and inline comments, and each must be finalized exactly once. If batches are not supported, compilation/runtime validation should reject max > 1.

Acceptance criteria

• Two body-only calls targeting distinct PRs produce two correctly paired reviews.
• Mixed body-only/inline review calls cannot share context across PRs.
• Finalization fails any accepted message that is not submitted.
• Summary and manifest record one result per call.
• Until multi-target buffers exist, reject submit-pull-request-review.max > 1 with an actionable error.

Downstream: Volaris-AI/project-template#4318.