feat: add optional Cua Driver computer backend

[f-trycua]

What this changes

Adds an opt-in COMPUTER_BACKEND=cua-driver implementation behind the existing computer-service contract. Playwright remains the default.

The Cua Driver backend:

• uses semantic browser snapshots and refs for read, click, type, and key actions;
• preserves the existing HTTP, WebSocket, token, takeover, shell, and per-Bot APIs;
• keeps isolated browser profiles under PROFILES_DIR/cua-driver, separate from Playwright profiles;
• uses native window screenshots and native input for takeover actions; and
• runs in both the standalone agent-computer image and the all-in-one production image.

The production packaging starts Xvfb and Openbox only for the Cua backend. It keeps Chromium and the display under pwuser, waits for graceful browser/profile shutdown before stopping X11, and builds both container paths in CI.

Where it runs

• New state that outlives a request? No new distributed request state. The backend uses the existing per-Bot computer lifecycle. Durable browser data lives in the mounted profile root under PROFILES_DIR/cua-driver; live Cua sessions remain process-local, like the existing live Playwright browser.
• What happens on the second replica? Multi-replica behavior is unchanged. Each agent-computer replica owns the browsers and profiles assigned to that deployment instance; the supervisor's per-Bot container model remains the isolation path.
• Anything serialised? No new cross-process serialization or database writes. The manager deduplicates concurrent starts for one Bot inside its process, and each isolated named profile remains owned by that computer instance.
• Anything fanned out to a browser? The existing gateway and WebSocket screen path are unchanged. Frames and takeover input still use the current computer-service endpoints.
• New listener, port, or schedule? None. The computer service remains on port 4100 inside the deployment boundary, and the all-in-one image still exposes only port 3001.

Boundary and audit

• Every acting call still goes through the existing gateway: resolve, decide, audit, then act.
• Backend refusals and failures return through the existing computer endpoints, so the gateway retains the same audit path.
• The backend does not add client-trusted identity or policy inputs. Direct computer-service requests still require COMPUTER_TOKEN.

Changelog

• No changelog entry: deployment behavior is unchanged unless an operator explicitly sets COMPUTER_BACKEND=cua-driver. The new configuration and operational differences are documented in the README and deployment, configuration, and architecture guides.

Known limitations

• Linux semantic clicks use a background-safe synthetic DOM event. Controls that require a trusted browser gesture may reject it.
• Cua profiles do not apply OpenBot's per-Bot egress proxy settings yet; the API reports egress: null for this backend.
• Ref-scoped key actions support Enter and printable characters. Arrows and editing keys use the native window route without a ref.

Proof

Candidate: 53e5a8868ee85ea5131ea89d6353c1685b849eab

• Formatting and lint passed. Lint reported only pre-existing warnings.
• Workspace and agent-computer typechecks passed.
• Production build passed.
• agent-computer: 99 tests passed.
• Current-main database suite: 752 tests passed, with five deployment-smoke skips.
• Both agent-computer/Dockerfile and the root production Dockerfile built successfully from the candidate.
• Standalone Cua smoke: navigation, semantic read/snapshot refs, isolated profile, and native PNG screenshot passed.
• Standalone default smoke: Playwright navigation passed, with no Xvfb or Openbox process started.
• All-in-one Cua smoke: Xvfb, Openbox, Bun, and Chromium ran as pwuser; navigation and native screenshot passed.
• Graceful shutdown smoke: docker stop --timeout 20 logged SIGTERM: closing the browser so its profile is flushed before X11 exited.
• Claude Code Fable reviewed the implementation and final integration delta. All must-fix findings were closed, and its final verdict was READY TO SUBMIT.

[Hotragn]

Not a review of the Cua backend itself — a note on the CI hunk, which closes something I had found
separately and was about to file. Worth saying so that it does not get filed as a duplicate, and that
the part this does not reach does not disappear with it.

The two lines that matter:

- run: bun install --frozen-lockfile && bun run typecheck
  working-directory: agent-computer

agent-computer ships "typecheck": "tsc --noEmit" (agent-computer/package.json:9), and root
typecheck is bun run --filter '*' typecheck over workspaces: ["app", "server", "worker"], so that
script had never run in CI — the package holding the only spawn in the deployment. Same for the
lockfile: agent-computer/bun.lock is committed and every install of it was plain bun install, which
Dockerfile:24-25 argues against in its own words about Bun's version ("an image built next month is
not the image built today") twenty-three lines above the install it did not apply to. Your comment
gets the reason right too: outside the workspaces deliberately, because it is built as its own image.

I checked it is free rather than assuming — bunx tsc --noEmit in agent-computer is clean on main
today, so nothing was being hidden, and bun install --frozen-lockfile there resolves 63 packages, so
the lockfile is valid as committed.

What the same reasoning still leaves open, after this lands:

	typecheck	--frozen-lockfile
agent-computer	this PR	this PR (Dockerfile:49, agent-computer/Dockerfile:15)
supervisor	still nothing — supervisor appears nowhere in ci.yml	still bun install (supervisor/Dockerfile:14)
agent-bot	no script to run	still bun install (agent-bot/Dockerfile:9)
agent-langgraph	no script to run	still bun install (agent-langgraph/Dockerfile:9)

supervisor is the closer parallel: it has the identical "typecheck": "tsc --noEmit"
(supervisor/package.json:9), it is equally outside workspaces, and it is the only thing in the
deployment holding a Docker socket (supervisor/Dockerfile:1). Both of its gates are also free today —
bunx tsc --noEmit clean, --frozen-lockfile resolves 73 packages. #40 touches
agent-bot/Dockerfile but only adds USER bun, so that install line is untouched by anything open.

I am not suggesting you widen this PR — the Cua backend is the change, and supervisor has nothing to
do with it. Happy to send the remainder as its own small PR once this is in, so it rebases onto your
ci.yml hunk rather than racing it. If you would rather carry it here, that is fine too; I would just
rather it be decided than dropped.