capwallet/v0 package

Package capwallet issues narrow, bounded, revocable capabilities to agents — instead of handing an agent a wallet key and hoping its prompt stays safe.

The demo makes three ideas that are usually conflated stand apart:

• identity — "this is agent Percy"
• authorization — "Percy may call this function on this realm"
• approval — "Percy may do it at most N times, for ≤ M coins, before block H, and I can revoke it at any moment"

A capability is the third thing: a least-privilege grant with a ceiling, an expiry, a use counter and a kill switch. Other realms consult Authorized() before honoring an agent action; the granter revokes with one call the instant something looks wrong.