Add file upload: setfiles (known input) + upload (file chooser)

[motin]

Adds Playwright-style file upload — the one capability missing for forms that take attachments.

Why

App Store Connect's "Reply to App Review" has an "Attach File" button that opens a transient file input via a native chooser. We couldn't upload because (a) the CLI had no file-set command, (b) setting the static input[type=file] via JS/DOM.setFileInputFiles does not route through the React handler — the button creates+clicks its own input, and (c) the file the button uses only exists while the chooser is open. The robust fix is to intercept the chooser, exactly like Playwright's fileChooser / setInputFiles.

What

Two entry points, mirroring Playwright's two paths. Both end in DOM.setFileInputFiles (a file input's .files is read-only to page JS, so eval/value-setters can't populate it; CDP can, and fires trusted input/change):

• setfiles -s <session> <ref> <path…> — set files on a known, snapshot-able <input type=file>. Resolves the ref to a RemoteObject (objectId), validates it's a file input (else errors pointing at upload), and sets files.
• upload -s <session> --click <ref> <path…> — arm Page.setInterceptFileChooserDialog, click the trigger, wait for Page.fileChooserOpened, then DOM.setFileInputFiles({ backendNodeId, files }), then disable interception. Handles the transient-input / custom-button case (ASC "Attach File", React dropzones).

Paths resolve from cwd and are validated to exist; multiple paths upload as a multi-file selection.

Implementation

• New src/core/upload.ts (setFilesByRef, uploadViaChooser); findRefExpr added to dom.ts to resolve a ref to an object handle. Commands in src/commands/{setfiles,upload}.ts, registered in index.ts. Reuses the existing per-target CDP core (no hand-rolled socket — that's what avoids the Origin 403 from Chrome).
• README + SKILL.md document both paths and when to use which. Also syncs the stale package-lock.json version to match package.json.

Validation

npm install && npm run typecheck && npm run build clean. Ran the build (node dist/index.js …) against a scratch tab with custom HTML containing both a static <input type=file> and a button that creates+clicks a transient input:

• setfiles e1 <file> → static input's change handler fired (filename+size observed).
• upload --click e2 <file> → transient input's change handler fired (filename+size observed).
• Multi-file, wrong-element (button → helpful error), missing-file, and missing---click all behave correctly. No live tabs touched.

🤖 Generated with Claude Code

[motin]

Follow-up from a real App Store Connect run (commit e371f5b).

upload --click reported success but nothing staged. Root cause: ASC's "Attach File" creates a transient <input type=file>, .click()s it, and never appends it to the document, reading it through a delegated change handler (React-style). DOM.setFileInputFiles sets .files and fires change, but on a detached node that event has no document ancestors to bubble through, so the delegated handler never runs. A node-bound listener fires while detached; a delegated one doesn't — which is exactly why the original synthetic test (direct addEventListener on the input) passed and ASC didn't.

Hardening, after setFileInputFiles:

• Resolve the backendNodeId to a live handle and verify (isConnected, files.length).
• If detached, re-attach the input (hidden) to the document and re-dispatch bubbling input+change so delegation / React onChange fires.
• Return {count, connected, reconnected}; the command now fails (exit 1) when count===0 instead of claiming success, and notes when it had to reconnect.

Validated against a repro covering direct-vs-delegated × detached/removed/stays. Caveat noted in the thread: if a page delegates at a deep container that isn't an ancestor of document.body, the body re-attach won't reach it — pending a live ASC confirmation.