v0.12.287 — live model catalog

Live model catalog

Prices and new models follow the gateway without a ClawRouter release.
The proxy now reads the active gateway's model listing (/v1/models) at
start and every 5 minutes:

• Prices and context limits of known models track the gateway.
• New chat models the gateway lists can be picked by name. They are never
  routed to automatically until they are added to ClawRouter on purpose.
• Aliases, the free models and their order, and every model's capabilities
  stay as ClawRouter defines them.

Built through @blockrun/model-catalog (bundled), and it does not touch
payment signing.

• Only ClawRouter's own free/* models count as free for maxCostPerRun
  and the balance check. A model the gateway lists as free is priced at 0, but
  its real price is still checked when the gateway asks for payment.

• If the listing cannot be fetched or read, the last good catalog is kept and
  the failure is logged once.

• No request goes anywhere but the gateway you already use. A remote ordering
  policy is opt-in through BLOCKRUN_MODEL_CATALOG_URL.

• Thanks to @KillerQueen-Z for the live catalog (#413).