feat(app,cli): camera + file/PDF attachments with HEIC/size normalization

[jlixfeld]

Summary

Extends the existing expImageUpload attachment pipeline (gallery images only today) to the full scope of #1319:

App (packages/happy-app)

• Attachment source chooser — the picker button now offers Photo Library / Take Photo / Choose File on native (web keeps direct picking; paste/drag already worked)
• Paste from clipboard (iOS/Android) — when the clipboard holds an image, the native chooser shows a Paste from Clipboard row, gated by Clipboard.hasImageAsync so it only appears when relevant (and stays silent until tapped — no premature iOS paste banner). Pasted bytes are staged to a cache file (the upload path needs a file:// URI) and run through the same normalize/thumbhash/upload pipeline as picked images. Web already had its own paste listener.
• Camera capture via expo-image-picker launchCameraAsync + camera permission flow (NSCameraUsageDescription added)
• File attachments via expo-document-picker (already a dependency, previously unused) — flows through the existing encrypted-blob upload and t:'file' session-event path unchanged
• Image normalization before upload (attachmentNormalize.ts):
  • HEIC/unsupported formats → JPEG q0.9 — fixes silent HEIC drop: the CLI's magic-byte check (detectClaudeImageMime) skips HEIC with only a debug log today, so iPhone photos often never reach the model
  • Downscale only when long edge > 1568 px (the Claude vision API ceiling — larger is discarded server-side anyway, and >5 MB images are rejected outright)
  • PNGs stay PNG (lossless, keeps screenshot transparency); in-range supported images pass through untouched
• i18n for all new strings across all 10 locales; settings label updated to “Attachments”

CLI (packages/happy-cli)

• Attachment→content-block conversion extracted to attachmentContentBlocks.ts and extended beyond images:
  • %PDF- magic → document content block
  • text/* mime / known text extension / clean UTF-8 → fenced text block with filename
  • anything else → visible notice in the message ([Note: attachment(s) … were omitted]) instead of today's silent drop
• Routing decisions are made on decrypted bytes, not the wire mimeType (iOS pickers lie)

Tests

• attachmentNormalize.spec.ts — 7 cases for the normalization decision logic
• attachmentContentBlocks.test.ts — 7 cases (image/PDF/text/extension-fallback/unsupported-notice/empty/HEIC)
• pnpm typecheck clean in happy-app; happy-app suite 594 passed; pre-existing codex/integration failures in happy-cli are untouched by this PR (no src/codex files in the diff)

Test plan

• Unit tests above
• Manual on-device: gallery image, camera photo, PDF, text file, unsupported binary → notice
• Manual on-device: copy an image elsewhere → open chooser → Paste from Clipboard row appears → attaches and uploads

Closes #1319. Related: #1270, #919, #70.

🤖 Generated with Claude Code

[jlixfeld]

Heads-up for maintainers on the feature flag: the expImageUpload toggle in settings/features.tsx (around line 108 on main) is currently commented out with {/* Image upload hidden — broken, shipping next release */}.

This PR is aimed squarely at the "broken" part — it fixes the silent HEIC drop (the most common failure on iOS, since the gallery/camera hand back HEIC that the CLI's magic-byte check skips) and adds the camera + file/PDF sources. Once this lands, re-enabling that <Item> should be safe, so the feature becomes reachable without a code edit.

I deliberately did not un-comment it in this PR to keep the diff focused on functionality and let you decide the release timing. Happy to either flip it on here or leave it for a follow-up — your call.