docs(arch): ConnectionCredentials decouples dial from call protocol (ADR-091) + migration plan cleanups

ADR-091: ConnectionCredentials — decouple the dial credential bundle
from the call protocol. CallCredentials (call-protocol-level, carries
auth_token) was being used as the dial's credential type, coupling the
dial to the call protocol. The auth_token is a hub-layer identity
correlation mechanism (browsers, alknet/register), not a transport
credential. ConnectionCredentials (transport-level: local_identity +
remote_identity) is the dial's credential bundle; all three dial
signatures unify on &ConnectionCredentials; dial_iroh's node_id
parameter is derived from remote_identity.fingerprint. CallCredentials
stays in alknet-call with auth_token. The shape is validated by the
future dial_ssh pattern (russh's check_server_key + authenticate_publickey
consume the same two dimensions).

Amends ADR-089 §3 (dial signatures) and §5 (move consequence), ADR-087
(input framing). Updates client/tls/call/core crate specs and the
extraction plan's Phase 0/3/4/5.

Migration plan cleanups (findings.md):
- Remove duplicated ordering-rationale bullets (copy-paste artifact)
- TL;DR: six phases -> seven (Phase 0 promoted); four compilable
  intermediate states -> each phase leaves workspace compilable
- Remove inline 'Wait — that's 10, not 8' self-correction; fix
  Category B header to (10 tests)
- Replace contradictory line ranges in Net Phase 5 test impact with
  name-based references
- Decide quinn feature fate: removed (not no-op)
- Note webpki-roots always-present per ADR-088 §5 in Phase 1 dep list

docs/architecture/crates/core/README.md

@@ -15,10 +15,12 @@ vestigial); core no longer carries the accept-loop runner or its
 transport deps (quinn, iroh, rcgen, rustls-acme).
 `Connection::from_quinn` / `from_iroh` stay in core's `types.rs` as
 shared constructors (gated on core's `quinn` / `iroh` features).
-`CallCredentials` and `RemoteIdentity` move to `alknet-core` (from
-`alknet-call`, per ADR-089 §5) — both the call and channels clients
-need them, and the dial (`alknet-client`) must not depend on the call
-protocol for the credential type.
+`ConnectionCredentials` and `RemoteIdentity` move to `alknet-core`
+(from `alknet-call`, per ADR-091) — the transport-level credential
+bundle consumed by the dial (`alknet-client`) and by server-side
+transport construction. `CallCredentials` (the call-protocol credential
+bundle, including `auth_token`) stays in `alknet-call` — the dial does
+not carry call-protocol dimensions.
 
 ## Documents