Identities for entities did.bot

feat(spaces): serve the core space XRPC surface #2584

targeting main from xrpc
Closed opened by and assigned to borel-balisong.test.pds.did.bot
targeting main from xrpc

Adds space-credential authentication, space writes and reads with MAC headers, simplespace reads, and the space OAuth scope ceiling, wired to the durable store at startup.

Co-Authored-By: Claude Code noreply@anthropic.com

Commits 9

feat(spaces): serve the core space XRPC surface
feat(spaces): add the durable space store
test(spaces): cross-check the protocol crate against the TypeScript reference
feat(spaces): give every account a P-256 KEM key
test(agentd): use a genuinely unread scope in the audit test
feat(spaces): add the space OAuth scope grammar
feat(spaces): vendor the space and simplespace lexicons
fix(spaces): apply the protocol crate's security review
feat(spaces): add the protocol primitives crate