fix(acp-server): include full bash command in permission requests

Problem

ACP session/request_permission for a Bash tool call only shows the first 50 characters of args.command, followed by … if longer. Custom ACP clients (the only ACP consumers right now is the JetBrains plugin) cannot see the rest of the command before deciding to allow/deny.

Where the truncation happens

packages/agent-core-v2/src/agent/tools/os/bash/bashTool.ts builds the ToolInputDisplay:

const preview = args.command.length > 50 ? `${args.command.slice(0, 50)}…` : args.command;
return {
  description: `Running: ${preview}`, // ← 50-char preview
  display: {
    kind: 'command',
    command: args.command,                // ← full command is here
    cwd, description, language: 'bash',
  },
 ...
};

AgentToolApprovalService.requestToolApproval forwards both action (= description, with preview) and display (= full command) into ApprovalRequest.

packages/acp-server/src/approval.ts:buildPermissionToolCallUpdate builds the toolCall for the ACP client:

content.push({
  type: 'content',
  content: { type: 'text', text: `Requesting approval to ${req.action}` },
});

The req.display (which carries command: <full>) is fed through displayBlockToAcpContent in packages/acp-server/src/convert.ts, which only handles diff / file_io / plan_review. kind: 'command' returns null and is dropped.

Net effect on the wire

• toolCall.title = "Bash"
• toolCall.content[] = a single text entry: "Requesting approval to Running: <first 50 chars>…"

The full args.command never crosses the ACP wire. Clients cannot display it, copy it, or render it in a terminal preview.

Proposed fix

Add a kind: 'command' branch to displayBlockToAcpContent that projects block.command into a ToolCallContent text entry:

if (block.kind === 'command') {
  return { type: 'content', content: { type: 'text', text: block.command } };
}

No change to the Bash tool itself — description (the 50-char preview) stays as the one-line summary; display.command is the full form for the approval card.

Test plan

• packages/acp-server/test/convert.test.ts: new describe('displayBlockToAcpContent') block; verify a command block renders to a text content entry whose text equals block.command; verify a command block with cwd / description does not crash and ignores those.
• packages/acp-server/test/approval.test.ts: extend the existing buildPermissionToolCallUpdate coverage to assert content[] contains the full command.
• packages/acp-server/test/e2e-turn.test.ts: scripted LLM issues a Bash call; the captured requestPermission payload's toolCall.content[] contains the full command.

Risk

Pure additive on the wire (a new content entry). Existing clients ignore unknown content kinds. The 50-char description in action is unchanged — only the content[] gains a new entry.

Start in packages/acp-server/src/convert.ts and inspect displayBlockToAcpContent, then review the existing coverage in packages/acp-server/test/convert.test.ts. Add coverage for command displays and extend packages/acp-server/test/approval.test.ts and packages/acp-server/test/e2e-turn.test.ts to verify the full command reaches the ACP permission payload. Done means command content includes block.command while cwd and description do not cause failures.