fix: stub isReadOnly on ACP queued-tools test mock

[AryanNandanwar]

Description

Fixes the Unit Tests & Coverage Analysis failure on Nano-Collective/nanocoder#887.

Timeline capture in runAcpConversation now calls toolManager.isReadOnly() before executing a tool. The acp-queued-tools spec mock did not implement that method, so four tests rejected with:

TypeError: toolManager.isReadOnly is not a function

• runAcpConversation - abort marks announced-but-unrun calls failed
• runAcpConversation - an announced call is never sent as tool_call twice
• runAcpConversation - a single tool call is still announced as tool_call
• runAcpConversation - the queued announcement carries no content

The mock now matches acp-conversation.spec.ts: write_file and execute_bash are treated as mutating; everything else is read-only.

Merge this into agent-action-timeline-undo to re-run CI on Nano-Collective#887.

Type of Change

• Bug fix
• New feature
• Breaking change
• Documentation update

Changeset

• Docs-only / test-only change; no changeset needed.

Testing

Automated Tests

• The previously failing source/acp/acp-queued-tools.spec.ts tests now pass
• Related ACP specs pass (acp-conversation, acp-timeline, acp-agent) — 82 tests
• All existing tests pass (pnpm test:all completes successfully)

Manual Testing

• Tested with Ollama
• Tested with OpenRouter
• Tested with OpenAI-compatible API
• Tested MCP integration (if applicable)

Checklist

• If this was for an open issue, I was assigned to it
• Code follows project style guidelines
• Self-review completed
• Documentation updated (if needed)
• No breaking changes (or clearly documented)