fix(opencode): suppress internal compaction output in ACP

[IsaacGao]

Issue for this PR

Related to #40494. This does not close it: it takes a different (narrower) approach than the one suggested in the issue.

Type of change

• Bug fix
• New feature
• Refactor / code improvement
• Documentation

What does this PR do?

Auto-compaction creates an internal assistant message with summary: true. The ACP layer forwarded its text and reasoning parts to chat clients as ordinary agent output because the ACP part-metadata cache never tracked the summary flag, so both live message.part.delta updates and session/load replay leaked internal compaction content.

This patch filters internal summaries directly, rather than passing a summary marker through ACP or adding lifecycle notifications as suggested in #40494. No public ACP protocol field is added, and compaction plus summary storage are unchanged.

• packages/opencode/src/acp/session.ts: add an optional summary boolean to KnownMessagePartMetadata and RecordPartMetadataInput, and persist it in recordPartMetadata.
• packages/opencode/src/acp/event.ts:
  • When part metadata is read from a full message, record summary = role === "assistant" && info.summary === true explicitly (false for other messages), so "known non-summary" is distinct from "not yet inspected".
  • Before forwarding a live delta, reuse cached metadata only when role, part type, and the summary decision are all known; otherwise fetch the owning message. Summary parts are never sent as agent_message_chunk or agent_thought_chunk. A reasoning part.updated still caches role: "assistant", so the summary decision is re-derived instead of trusted from that cache.
  • replayMessage keeps recording part metadata but skips replaying the content of a summary assistant message, so later deltas for those parts stay filtered.

#42316 fixes the same class of leak for CLI JSONL output; this patch covers the ACP path.

How did you verify your code works?

Added regression tests in packages/opencode/test/acp/event.test.ts:

• live summary text deltas and reasoning deltas are suppressed;
• suppression survives cache reuse and a later part.updated;
• session/load replay suppresses summary text and reasoning;
• normal assistant replies after compaction still stream (replayed text, replayed reasoning, and a live delta);
• a normal reply whose body contains the word "summary" is not filtered;
• summary filtering stays isolated per session.

Existing tests that build known normal part metadata directly now record summary: false, and the reasoning-delta service test provides a message fixture instead of weakening the filter.

On this machine with Bun 1.3.14 and locked dependencies:

• bun test test/acp/ --timeout 30000 --only-failures -> 146 pass, 0 fail.
• bun typecheck -> clean.
• The new regression tests fail on the unpatched code and pass with the patch.
• Prettier and git diff --check clean.

Not verified against a real chat client deployment (e.g. a bridge forwarding ACP updates).

Checklist

• I have tested my changes locally
• I have not included unrelated changes in this PR

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This PR doesn't have a linked issue. All PRs must reference an existing issue.

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1. Open an issue describing the bug/feature (if one doesn't exist)
2. Add Fixes #<number> or Closes #<number> to this PR description

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