docs: ADR-049/050 in indexes; changelog link refs; ported-ADR range 001..048

- architecture README: index rows for ADR-049 (establishment phase) and
  ADR-050 (pump_bidi); stale ADR-001..045 range labels corrected
- channel-operations.md: design-decision table + references list the
  two new ADRs
- CHANGELOG: missing link references for 0.4.0/0.4.1/0.5.0/0.6.0
- AGENTS.md: ADR range 001..050

docs/architecture/channel-operations.md

@@ -470,6 +470,8 @@ All design decisions are documented as ADRs in [decisions/](decisions/).
 | [035](decisions/035-channels-pure-channel-multiplexing.md) | Pure Channel Multiplexing | No stream_types; handler owns sub-mux |
 | [021](decisions/021-streaming-handler-for-subscriptions.md) | StreamingHandler | The machinery `channel/resources/subscribe` uses |
 | [046](decisions/046-publish-operation-type-and-handler-kind-sink.md) | Pub Operation Type | The `Pub`/`Sub` primitives the per-ALPN open ops build on |
+| [049](decisions/049-channel-open-establishment-phase.md) | Channel-Open Establishment Phase | The establisher hook; typed `channel:open_failed`; `Establishment.plan` (amendment 2); the `JoinHandle` lifetime contract |
+| [050](decisions/050-pump-bidi-two-pump-helper.md) | `pump_bidi` Two-Pump Helper | The data-plane helper openable-ALPN handlers await inline |
 | [026](decisions/026-forwarded-for-identity.md) | Forwarded-For Identity | The auth chain for hub-relayed opens (and why the cap is per direct-caller, not per `forwarded_for`) |
 | [011](decisions/011-dynamic-resource-ownership-for-runtime-spawned-resources.md) | Dynamic Resource Ownership | The parallel — a channel slot is a resource, the cap is a quota check; `resource_id_path` works again under per-ALPN ops |
 
@@ -477,6 +479,9 @@ All design decisions are documented as ADRs in [decisions/](decisions/).
 
 - ADR-047: openable ALPNs are operations (the unifying ADR — per-ALPN
   open ops, `channel_open` marker, `ChannelCore` wrapper, opener ledger)
+- ADR-049: channel-open establishment phase (the establisher hook,
+  `channel:open_failed`, the plan payload)
+- ADR-050: `pump_bidi` (the two-pump helper)
 - ADR-037: channel lifecycle operations (amended by ADR-047)
 - ADR-041: per-identity channel cap (amended by ADR-047 §7 — opener
   ledger, every teardown path)