fix(opencode): batch direct shell output updates

[flowluap]

Issue for this PR

Closes #37787

Type of change

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

What does this PR do?

The direct user shell awaited a durable part update for every decoded output chunk. This coupled pipe consumption to SQLite projection and event broadcast work.

This change consumes output immediately and publishes the latest cumulative running snapshot at most every 100 ms. A version counter keeps output dirty when bytes arrive during an update. The publisher is interrupted before the existing final part update, so completion remains authoritative and no running update can arrive afterward.

How did you verify your code works?

• bun test test/session/prompt.test.ts: 59 pass, 1 platform skip
• Package typecheck and full commit-hook monorepo typecheck: 30 successful packages
• Prettier and git diff --check
• 20 paced writes: 4 running updates instead of up to 20 (80% fewer)
• Durable event payload: 9,156 bytes to 3,128 bytes (65.8% lower)
• Final output remained byte-for-byte complete

Screenshots / recordings

N/A

Checklist

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

[github-actions]

The following comment was made by an LLM, it may be inaccurate:

I found a related PR that appears to be a near-duplicate:

Related PR:

• PR fix(opencode): batch shell output updates #37653 - fix(opencode): batch shell output updates
  • fix(opencode): batch shell output updates #37653

Why it's related:
This PR also addresses batching of shell output updates, which is very similar in scope to PR #37788 (fix(opencode): batch direct shell output updates). The main difference appears to be that #37788 specifically targets "direct" shell output, while #37653 may have addressed a broader shell output batching issue. You should verify whether these PRs handle different code paths or if one supersedes the other.

[flowluap]

Related, but they cover separate implementations:

• fix(opencode): batch shell output updates #37653 changes packages/opencode/src/tool/shell.ts, the agent-invoked ShellTool path.
• This PR changes packages/opencode/src/session/prompt.ts, the user-invoked direct ! shell path.

The paths do not call each other and the PRs have no overlapping files. Merging #37653 does not change the per-chunk sessions.updatePart calls in the direct shell path. The same 100 ms batching policy is intentional so both shell implementations avoid coupling pipe consumption to durable updates. They can be reviewed and merged independently.