feat(gateway): suggest URL from clipboard on Gateway step (issue #18)

[johnnyhuy]

Closes #18.

Summary

When the user lands on the Gateway step in the Electron app, Hoist reads the clipboard (renderer-initiated only — main never polls) and offers a one-click "Use this URL" suggestion pill below the Base URL field if the clipboard contains a parseable URL. Single-call, single-click; user editing the input discards the suggestion.

What changed

• src/shared/channels.ts — new channel clipboard:read

• src/main/ipc.ts — handler uses clipboard.readText(), trims, truncates at 4096 chars

• src/preload/api.ts + src/preload/index.ts — typed ClipboardReadResponse + window.hoist.clipboard.read()

• src/renderer/App.tsx

  • extractBaseUrl() regex: ^https?://[^\s/?#]+ — accepts scheme+host only (no path/query/fragment)
  • GatewayStep calls clipboard.read() on mount
  • "Use this URL" pill below the Base URL input with ✕ dismiss button
  • Editing the Base URL field clears the suggestion (one-shot)

• scripts/test-extract-base-url.mjs — 10-case smoke test mirroring the App.tsx regex

• package.json — test:extractor script

• .github/workflows/ci.yml — runs npm run test:extractor in the app job between lint and build

Privacy

• The renderer is the only caller of clipboard.read. Main process never reads the clipboard opportunistically.
• Reading only happens after the user lands on the Gateway step (one call, gated by mount).
• Output is truncated to 4096 chars; no autosave, no sharing.
• Write access never requested (no clipboard.writeText added).

Verification

• npm run typecheck ✓
• npm run lint ✓
• npm run test:extractor ✓ (10/10 cases including wikipedia URL → host-only)
• npm run build ✓
• Screenshot above shows the pill with the parsed URL inline, edit clears it, ✕ dismisses it

Test cases that pass

✓ "https://gateway.acme.com"                                           → "https://gateway.acme.com"
✓ "http://localhost:4000/"                                             → "http://localhost:4000"
✓ "https://gateway.ai.cloudflare.com/v1/<account_id>"                 → "https://gateway.ai.cloudflare.com"
✓ "\n  https://api.example.com/v1  \n"                                 → "https://api.example.com"
✓ "mailto:nope@example.com"                                           → null
✓ ""                                                                   → null
✓ "https://"                                                            → null
✓ "api.example.com"                                                    → null
✓ "https://example.com/with/path"                                      → "https://example.com"
✓ "https://en.wikipedia.org/wiki/Claude_(language_model)"              → "https://en.wikipedia.org"