chore: merge upstream opencode v1.2.20

[kulvirgit]

Summary

• Merge upstream opencode v1.2.20 (from v1.2.18 base)
• Resolved 4 conflicts: package.json version, agent.ts bash streaming, auth.ts + worker.ts new imports
• Fixed merge script to keep upstream packages instead of deleting them
• Regenerated bun.lock

Upstream changes (v1.2.18 → v1.2.20)

• Bash output streaming in ACP agent
• Replaced Bun-specific APIs with Node.js equivalents (Bun.hash, Bun.write, Bun.sleep, Bun.stdin, etc.)
• Git fsmonitor daemon leak fix
• GPT-5.4 model support

Test plan

• bun run build passes
• bun test — 1432 pass, 51 fail (same as main, no new failures)
• Typecheck — only pre-existing plugin/index.ts error (same as main)

[sentry]

Bug: The content variable, holding bash output, is created but not included in the sessionUpdate payload, preventing the output from being streamed to the client.
_{Severity: CRITICAL}

Suggested Fix

Add the content variable to the update object within the this.connection.sessionUpdate call in the case "running" block. The line should be content, inside the update object literal.

Prompt for AI Agent

Review the code at the location below. A potential bug has been identified by an AI
agent.
Verify if this is a real issue. If it is, propose a fix; if not, explain why it's not
valid.

Location: packages/opencode/src/acp/agent.ts#L346-L348

Potential issue: In the `handleEvent` function, the `case "running"` block for tool
calls correctly populates a `content` variable with new bash output. However, the
subsequent `this.connection.sessionUpdate` call that sends the update to the client
omits this `content` field from its payload. As a result, while the logic for detecting
new output and de-duplicating it is present, the actual output content is never
transmitted. This effectively breaks the bash output streaming feature, as the client
will not receive any updates for running commands.