Mobile: "Add to another machine" from the new task Environment picker

[mrevanzak]

The problem

On web and desktop, the composer's Run on menu has Add to another machine. It clones the current project onto another connected machine, copies the ignored files you choose (.env files are preselected), and moves your draft there.

The mobile app has no equivalent. Its Environment picker for a new task only lists machines that already have the project. If I am on my phone and want to run a task on a machine that does not have the repo yet, I have to leave the draft, go through Add project, paste the remote URL by hand, pick a folder, and then retype the prompt. The .env files do not come along at all, so the clone usually cannot run until I get back to a desktop.

Phone-first use is exactly when this matters: the machine I want is often a server or a second computer I am not sitting at.

The proposal

Bring the same capability to the mobile Environment picker, reusing what mobile already has.

• Below the machine list, an Add to another machine section lists each connected machine that can clone the project and does not have it yet. It is hidden when the project has no git remote or no such machine exists, the same rule the web uses.
• Tapping a machine opens the existing Clone destination screen for it, with the project's remote URL and the default folder filled in.
• That screen also lists the source project's ignored files, with the same defaults as desktop: .env*, .envrc and .dev.vars preselected, files over 1 MB not selectable. They are copied after the clone finishes.
• After the clone starts, the app opens the draft on the new machine with the clone banner. Text and attachments already in the draft move with it.

Scope

• Mobile only. No server or contract changes: it uses the existing startProjectClone, listIgnoredFiles, readFile and writeFile calls that the web dialog uses.
• Not proposed here: the SSH/HTTPS clone protocol toggle from the desktop dialog. Mobile would clone with the project's own remote URL. I can add it if you want full parity in one change.
• Open PR fix(mobile): list all environments in new-task picker without silent retarget #29033 changes the same picker to list every environment. The two are compatible, but whichever lands second will need a small rebase.

Questions for maintainers

1. Is the Environment picker the right home for this on mobile, or would you rather it live somewhere else (for example the project overview in Settings)?
2. Should sends be held until the ignored files land, as the desktop composer does, or is a failure notice enough on mobile?

I have a working branch for the picker and clone flow and am happy to open a PR once the direction is approved.