docs: align remaining alloc-failure references with ADR-010 §2A (prepublish review for v0.3.0)

- README.md ADR index: ADR-010 status notes the §2A amendment
- ADR-009: amendment note records the §2A supersession (in-band path
  shrinks to nothing from registered producers)
- ADR-010 Consequences: dial_failed replaces the stale in-band
  allocate_failed retry-policy bullet
- AllocFailed doc comment + tty-backend.md: describe both failure
  surfaces (direct-path frame / channels-path dial_failed)

docs/architecture/README.md

@@ -37,7 +37,7 @@ tty-specific and therefore not ported into alktty's ADR range).
 | [007](decisions/007-tty-inside-channels.md) | TTY Inside Channels — Sub-Streams, Not Wire Format | alknet ADR-077 | Accepted (**reversed by ADR-008** — kept for historical context) |
 | [008](decisions/008-channels-pure-channel-multiplexing.md) | Channels Pure Channel Multiplexing (8-Byte Header, No `stream_type`) | alknet ADR-093 | Accepted (amends alknet ADR-071/074; reverses ADR-007) |
 | [009](decisions/009-channels-open-op-is-the-negotiation.md) | The Channels Open Op's `input` Is the Negotiation | alktty-native | Accepted (resolves review #001 L1; amended by review #002 R4 — parse failure is a client-visible error frame; amended by ADR-010 — semantic failures move into the establisher) |
-| [010](decisions/010-channels-establisher-migration.md) | Channels-Path Establishment Failures Move into an Establisher | alktty-native | Accepted (adopts alkcall 0.5.0 ADR-049; amends ADR-009's R4 amendment — in-band frames shrink to `allocate_failed`) |
+| [010](decisions/010-channels-establisher-migration.md) | Channels-Path Establishment Failures Move into an Establisher | alktty-native | Accepted (adopts alkcall 0.5.0 ADR-049; amends ADR-009's R4 amendment; amended 2026-09-07 §2A for alkcall 0.6's plan payload — allocation moves into the establisher, no in-band frame from a registered producer) |
 
 ## Key Design Principles
 

docs/architecture/decisions/009-channels-open-op-is-the-negotiation.md

@@ -21,6 +21,13 @@ cannot carry the allocated handle across — see ADR-010 §2). The R4
 tests that asserted the in-band frames for those classes now assert
 the call-error shape.
 
+Amended 2026-09-07 (ADR-010 §2A, alkcall 0.6.0 — review 007 R-01):
+`Establishment` gained its plan payload, so `allocate` also moved
+into the establisher — the in-band error-frame path on this channel
+shrinks to nothing from a registered producer (the frames remain the
+defense-in-depth fallback for no-establisher registrations and the
+direct path). See ADR-010 §2A.
+
 ## Context
 
 Before this ADR, the channels path carried the negotiation twice. The

docs/architecture/decisions/010-channels-establisher-migration.md

@@ -242,8 +242,9 @@ on `establishment_reason()` without unwrapping strings.
   open no longer allocates → succeeds → in-band-fails. Ledger, policy
   count, and manager state balance on every rejection.
 - Retry policy / UX can branch: `unknown_resource` (bad config — don't
-  retry), `timeout` (maybe retry), `allocate_failed` (capacity —
+  retry), `timeout` (maybe retry), `dial_failed` (capacity/target
-  still distinguishable in-band).
+  refused — maybe retry; amended §2A, was the in-band
+  `allocate_failed`).
 - The consumer's `open_via_channels` failure is a typed call error —
   no peeking at the data stream for anything but the (now
   unreachable-from-registered-producers) error-frame formality.

docs/architecture/tty-backend.md

@@ -125,8 +125,10 @@ pub enum TtyError {
 
 - `AllocFailed` — the PTY couldn't be allocated, the docker exec failed
   to start, the SSH channel request was rejected. Returned by
-  `allocate()`; the adapter sends `{"error":"allocate_failed",...}` and
+  `allocate()`; on the direct path the adapter sends
-  closes (tty-adapter.md §"Negotiation errors").
+  `{"error":"allocate_failed",...}` and closes (tty-adapter.md
+  §"Negotiation errors"); on the channels path the establisher maps it
+  to `channel:open_failed` / `dial_failed` (ADR-010 §2A).
 - `WaitFailed` — the backend couldn't reap the child / determine the
   exit code. Returned by the `exit_code` future; the adapter sends
   `{"type":"exit","code":-1}` (ADR-004 §4).

src/backend.rs

@@ -45,8 +45,11 @@ pub type BoxFuture<T> = futures::future::BoxFuture<'static, T>;
 #[derive(Debug, thiserror::Error)]
 pub enum TtyError {
     /// The PTY couldn't be allocated, the docker exec failed to start, the
-    /// SSH channel request was rejected. Returned by `allocate()`; the
+    /// SSH channel request was rejected. Returned by `allocate()`; on the
-    /// adapter sends `{"error":"allocate_failed",...}` and closes.
+    /// direct path the adapter sends `{"error":"allocate_failed",...}` and
+    /// closes; on the channels path (alkcall 0.6, ADR-010 §2A) the
+    /// establisher maps it to `channel:open_failed` /
+    /// `details.reason == "dial_failed"`.
     #[error("allocate failed: {message}")]
     AllocFailed { message: String },
     /// The backend couldn't reap the child / determine the exit code.