Run compact hooks for remote compaction v2

[jif-oai]

Why

Remote compaction v2 is the /responses implementation of session-history compaction, but it still needs to preserve the observable contract of the legacy /responses/compact path. In particular, users and integrations that rely on PreCompact and PostCompact hooks should not see different behavior when remote_compaction_v2 is enabled.

What Changed

• Runs PreCompact before issuing the remote compaction v2 request, including Interrupted analytics when a pre-hook stops execution.
• Runs PostCompact after a successful v2 compaction and aborts the turn if the post-hook stops execution.
• Adds compact_remote_parity coverage that compares legacy and v2 compaction across manual transcript shapes, automatic pre-turn compaction, automatic mid-turn compaction, hook payloads, replacement history, follow-up request payloads, and API-key service_tier=fast behavior.
• Registers the new parity suite under core/tests/suite.

Relevant code:

• compact_remote_v2.rs
• compact_remote_parity.rs

Verification

• Added core/tests/suite/compact_remote_parity.rs to assert parity between legacy remote compaction and remote compaction v2 for the affected request, hook, rollout-history, and follow-up paths.
• Existing compact_remote_v2 unit coverage still exercises v2 replacement-history retention and compaction-output collection.

[jif-oai]

@codex review

[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. Delightful!

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