fix(desktop): attach non-image web uploads by path instead of failing the read

[ashneil12]

Problem

In the hosted web rich-chat (vweb client), dropping a non-image file (.md, .txt, .pdf, …) fails with a "Drop files / Could not read <name>" toast. Images work; other files don't. The upload itself succeeds — the file lands at ~/.hermes/uploads/<date>/<name> and the chip shows that server path — but the attach then errors.

Root cause

The hosted web SPA has no local filesystem. A dropped non-image file is uploaded to ~/.hermes/uploads via the web shim and attached as a kind:'file' ref pointing at that server path. At submit/eager-upload time, uploadComposerAttachment re-read the bytes client-side via window.hermesDesktop.readFileDataUrl(serverPath).

But the web shim's readFileDataUrl only serves an in-memory cache that uploadBrowserFile populates for images only (web-shim.ts gates the cache write on image/*). So for any non-image file the read returns '' → null → throw new Error('Could not read ' + label) (use-prompt-actions.ts), where label is the server basename — exactly the toast in the screenshot. Images escape only because their bytes are cached at drop time.

Fix

In the hosted web client, skip the client-side byte read for non-image files and attach by path only. The file already lives on the gateway (~/.hermes/uploads, made agent-readable by the upload endpoint's chown), so file.attach resolves the path directly — _stage_session_file_attachment Case 2 reads the bytes and returns an @file: ref. No data_url round-trip, no 16 MB cap, no double upload.

• Native Electron remote mode is unchanged — its paths live on the client disk and still upload bytes.
• Gated on window.__HERMES_WEB_CLIENT__ (set by lib/web-shim.ts), matching the existing web-detection idiom.
• Verified end-to-end against the gateway: _resolve_attachment_path resolves any existing absolute file (no allowlist), so the uploads path resolves into Case 2.

Test

Adds a regression test: the web client attaches a non-image file by path, with no client read and no data_url, and returns the gateway @file: ref.

Rollout

Canary-first. After merge: publish a new canary image and redeploy a canary instance to verify a real .md drop, then port to prod.

[github-actions]

🔎 Lint report: fix/web-nonimage-attach-path-only vs origin/main

ruff

Total: 0 on HEAD, 0 on base (➖ 0)

🆕 New issues: none

✅ Fixed issues: none

Unchanged: 0 pre-existing issues carried over.

ty (type checker)

Total: 10932 on HEAD, 10932 on base (➖ 0)

🆕 New issues: none

✅ Fixed issues: none

Unchanged: 5741 pre-existing issues carried over.

Diagnostics are surfaced as warnings — this check never fails the build.