fix(serviceoffer): scope ERC-8004 agentId to the offer's own chain

[bussyjd]

Canary402 field report — issue 1 (🚨 ERC-8004 identity incorrectly reused across chains)

Switching an offer's spec.payment.network from Base Sepolia to Base retained the Sepolia numeric Agent ID and published it as a Base registration — a token that on Base may belong to a different wallet — and disabling registration left the wrong entry in status output.

Root cause

RegistrationRequest.status is never chain-tagged and never reset when spec.chain changes. Four sites trusted it (or the equally chain-blind offer.status.agentId) as an AgentID source: reconcileRegistrationStatus, reconcileRegistrationActive (whose firstNonEmpty fallback also skipped the entire on-chain ownership-verification block whenever the stale id was non-empty), reconcileRegistrationTombstone, and applySharedRegistrationStatus (which also flipped Registered=True off a bare non-chain-scoped phase/id — widened by 84dcbf8). The unverified id was then durably upserted into the shared AgentIdentity CR and rendered into /.well-known/agent-registration.json, with no removal path anywhere in the codebase.

Fix

• All four sites now derive AgentID solely from AgentIdentityAgentIDForChain(identity.Status, <the offer's own chain>); a chain switch therefore forces the existing on-chain ownership check (FindRegistrationByOwnerAndURI/ByTxHash) before anything is recorded.
• Registered=True requires a chain-scoped AgentID; status.registrationTxHash is only mirrored when one exists (same chain-blind source).
• Disabling registration clears status.agentId/registrationTxHash.
• New RemoveAgentIdentityRegistration counterpart to Upsert… + obol sell identity forget <chain> escape hatch so already-poisoned identity records can be corrected (previously permanent).

Tests

• Chain-switch regression test: recorded base-sepolia id + switch to base → nothing upserted for base, registration document unchanged (fails on pre-fix code with a spurious base entry).
• Shared/borrowing offer on a mismatched chain does not adopt the owner's foreign-chain id nor flip Registered.
• Disable-clears-status, RemoveAgentIdentityRegistration unit tests.
• go test ./... green; implementer verified both new regression tests fail when the two core lines are reverted.

Part of the Canary402 field-report sweep (6 PRs). Commit unsigned — batch re-sign before merge if required.

https://claude.ai/code/session_014YjPMViNrZ7zBVgUQzwEKk