Fix: restore Add photos & files in Pocodex

[xIGBClutchIx]

Summary

This restores Add photos & files in Pocodex so browser sessions open a working file chooser again and attach the selected files instead of failing with Unable to open file picker.

What changed

• add a browser-side attachment picker helper in the bootstrap script that returns the selected files in the shape the current Codex bundle expects
• patch extracted and cached webview attachment assets so non-file: browser sessions use that helper instead of the native pick-files route
• reuse in-memory image bytes for browser-picked image attachments so the bundle does not fall back to read-file-binary on files that only exist in the browser chooser
• add focused regression coverage for both freshly extracted and already cached webview bundles

Root cause

• Pocodex only handled the older hidden-input attachment path, but the current desktop bundle moved Add photos & files into a bundled pick-files flow
• in browser-served Pocodex, that native pick-files route is unsupported, so the composer surfaced Unable to open file picker
• image attachments also needed a browser-safe byte path because the bundle otherwise tried to read chooser-only files through the native binary file bridge

Impact

• Add photos & files opens a real browser file chooser again in Pocodex
• regular files and images attach to the composer without the picker error
• regression coverage now protects the extracted and cached webview patch paths this fix depends on

Validation

• pnpm run check:commit
• pnpm exec vitest run test/codex-bundle.test.ts
• pnpm exec tsx src/cli.ts --dev --listen 127.0.0.1:8799
• live local verification on http://127.0.0.1:8799/ that Add photos & files attaches README.md and artifacts/icon.png as composer chips without showing Unable to open file picker