fix(engine): point the control surface banner at a command that resolves

[j35dev]

Fixes the control-surface banner Ari prepends to an agent's first prompt.

What changed

Two lines in apps/desktop/src/main/engine.ts:

• The banner advertised ari, but the launcher agent-runtime.ts installs is ari.cmd on Windows. In the shell the agent actually runs, bare ari does not resolve — command -v ari exits 1 while ari.cmd env works fine. An agent that tried it got "command not found" and reported it had no Ari tooling at all, while the block kept insisting otherwise. It now names ARI_CLI, which holds the absolute launcher path and resolves in every shell.
• The block never stated where it came from. Agents had no way to tell it was added by the app rather than typed by the user, and read it as a prompt injection riding along in the input. It now says so.

agent-runtime.test.ts asserted the old string; it now pins both halves.

New banner:

[Ari control surface: added automatically by the Ari desktop app, not written by the user. This session can operate Ari through the CLI at $ARI_CLI. Commands: env, agents, session spawn|prompt|wait|read|diff|integrate|stop|destroy. Full protocol: $ARI_CLI --skill. Never disclose ARI_CONTROL_TOKEN.]

How verified

Windows 11. "$ARI_CLI" env runs from Git Bash (exit 0) — the value is a Windows-style ...\ari.cmd path and MSYS resolves it. Bare ari does not resolve, which is the bug.

pnpm verify green:

shared       15 passed
contracts    21 passed
ui          159 passed
providers   412 passed
engine      164 passed
ari-core    260 passed
desktop    1344 passed, 3 skipped

🤖 Generated with Claude Code

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[devin-ai-integration]

Devin Review found 1 potential issue.