feat(core): Add no-op finish tool.

[joshualitt]

TLDR

Adds a simple no-op finish tool behind an experimental setting.

Reviewer Test Plan

Download patch and attempt tasks.

Testing Matrix

	🍏	🪟	🐧
npm run	❓	❓	:heavy_check_mark:
npx	❓	❓	❓
Docker	❓	❓	❓
Podman	❓	-	-
Seatbelt	❓	-	-

Linked issues / bugs

A first attempt to resolve https://github.com/google-gemini/gemini-cli/issues/10505

[github-actions[bot]]

Size Change: +1.78 kB (+0.01%)

Total Size: 17.8 MB

Filename	Size	Change
./bundle/gemini.js	17.8 MB	+1.78 kB (+0.01%)

ℹ️ View Unchanged

Filename	Size
./bundle/sandbox-macos-permissive-closed.sb	1.03 kB
./bundle/sandbox-macos-permissive-open.sb	830 B
./bundle/sandbox-macos-permissive-proxied.sb	1.31 kB
./bundle/sandbox-macos-restrictive-closed.sb	3.29 kB
./bundle/sandbox-macos-restrictive-open.sb	3.36 kB
./bundle/sandbox-macos-restrictive-proxied.sb	3.56 kB

_{compressed-size-action}

[joshualitt]

@jacob314 , thoughts on the UI side of this? By default, we get a simple box with the summary from the agent.