v0.18.1

A reliability pass on the browser app: failures are no longer silent, mobile
subdomains work, and on-chain feedback actually lands. No SDK API changes.

Fixed

• Chat turns never fail silently anymore. A failed turn (proxy 402, bad
  key, RPC error) used to write the error to the terminal status line and leave
  a blank assistant bubble — the "blank entry, no feedback" black hole. Errors
  now render inside the transcript bubble with cause-specific guidance
  (credits/quota → check the account tab; auth → check your Gemini key), and a
  successful-but-empty stream prints an explicit "(empty response …)" note
  instead of a blank bubble.
• Mobile subdomains are no longer dead. Every seed-derived op on a subdomain
  (owner verify, Gemini-key restore, sponsored-tx signing) ran through a hidden
  cross-origin apex/?signer=1 iframe — which mobile browsers partition, so the
  embedded apex saw an empty OPFS and every op failed (the phone worked on the
  apex but not on its own subdomains). New seed_pull module copies the seed
  into the subdomain origin's OWN OPFS via a top-level apex round-trip (ECIES-
  sealed, each leg first-party so it works on mobile); verify.rs then runs
  every seed op LOCAL-FIRST off the local wallet and never touches the iframe.
• Credits stop fragmenting per origin. With the seed local on a subdomain,
  the credit signer uses the real master wallet instead of a throwaway
  per-origin device key — so redeemed $LH and the active session apply across
  all of a user's origins instead of each subdomain showing an empty balance.
• On-chain feedback submission actually lands. The sponsored
  submitFeedback tx was capped at a flat 800k gas; a short note needs
  ~1.3M and a long one up to ~17M (the facet stores the full string in cold
  SSTOREs), so every submission reverted out-of-gas — silently (the local
  .lh_feedback.txt mirror succeeded, the chain leg failed, feedbackCount
  stuck at 0). Gas is now scaled to the text length.