feat: rename ALPN prefix from alknet/ to alk/ (v0.1.1)

- CHANNELS_ALPN: b"alknet/channels" → b"alk/channels"
- CallAdapter::alpn(): b"alknet/call" → b"alk/call"
- derive_alpn_from_op_name: alknet/ prefix → alk/ prefix
- All ALPN string literals in src/ and docs/ updated
- ADR-004 amended with prefix rename rationale
- AGENTS.md, README.md updated
- Version bumped to 0.1.1

Review: docs/reviews/003-alpn-prefix-rename.md

Verification:
- cargo test: 542 passed, 0 failed
- cargo clippy --all-targets -- -D warnings: clean
- cargo fmt --check: clean
- cargo doc --no-deps: clean

docs/architecture/channel-operations.md

@@ -25,7 +25,7 @@ and/or `channels/<alpn>/pub`:
 | `channels/<alpn>/sub` | `Sub` | consumer (subscribes) | producer (streams) | server → client |
 | `channels/<alpn>/pub` | `Pub` | producer (publishes) | consumer (receives) | client → server |
 
-The `channels/<alpn>/...` path segment is the ALPN with the `alknet/`
+The `channels/<alpn>/...` path segment is the ALPN with the `alk/`
 prefix stripped (ADR-047 §"Negative"). An ALPN may register one or both
 ops; separate op types → separate ACLs. The op spec carries the
 `channel_open: Option<ChannelOpenSpec>` marker (ADR-047 §2) — the
@@ -44,8 +44,8 @@ Request (`call.requested` on channel 0):
 ```
 
 The `input` is ALPN-specific params (the former `params` field, now the
-op's `input_schema`). For `alknet/tty` this is the `NegotiateRequest`;
-for `alknet/tunnel` this is the target resource. The channels layer does
+op's `input_schema`). For `alk/tty` this is the `NegotiateRequest`;
+for `alk/tunnel` this is the target resource. The channels layer does
 not interpret `input`.
 
 Response (`call.responded`):
@@ -174,11 +174,11 @@ The responder registers a `StreamingHandler` that emits a
   "output": {
     "resources": [
       {
-        "alpn": "alknet/tty",
+        "alpn": "alk/tty",
         "backends": ["docker", "local"]
       },
       {
-        "alpn": "alknet/tunnel",
+        "alpn": "alk/tunnel",
         "targets": ["container:*", "service:postgres"]
       }
     ]
@@ -394,7 +394,7 @@ This is not a flaw — it is the same shape as any per-peer ACL.
 
 ### Recursive channels do not bypass the cap
 
-A recursive `alknet/channels`-inside-`alknet/channels` channel runs a
+A recursive `alk/channels`-inside-`alk/channels` channel runs a
 new `ChannelsAdapter` with a new `ChannelManager`. If the same
 `ChannelLifecyclePolicy` is wired into the inner `ChannelOperations`,
 the inner channels are counted against the same identity. Recursion
@@ -422,8 +422,8 @@ JSON payload; the hub's `CallAdapter` translates these too (rewrites
 `channel/control` — it's a call operation, translated, not
 byte-forwarded.
 
-The hub never runs a handler for `alknet/tty`, `alknet/ssh`, or
-`alknet/tunnel`. It runs `alknet/channels` (the relay) and `alknet/call`
+The hub never runs a handler for `alk/tty`, `alk/ssh`, or
+`alk/tunnel`. It runs `alk/channels` (the relay) and `alk/call`
 (for its own hub-level operations + translation). The `channel_open`
 marker (ADR-047 §2) is how the hub recognizes a channel-open op during
 `from_call` discovery (ADR-047 §1, Gap C) — the `from_call` relay
@@ -437,7 +437,7 @@ All design decisions are documented as ADRs in [decisions/](decisions/).
 |-----|----------|---------|
 | [037](decisions/037-channel-lifecycle-operations.md) | Channel Lifecycle Operations | The generic ops; `direction` pinned (amended by ADR-047 — `channel/open` dissolves; `direction` removed) |
 | [047](decisions/047-openable-alpns-are-operations.md) | Openable ALPNs Are Operations | Per-ALPN open ops; `channel_open` marker; `ChannelCore` wrapper; opener ledger |
-| [036](decisions/036-channel-0-pre-negotiated-call.md) | Channel 0 Pre-Negotiated | Channel 0 = alknet/call |
+| [036](decisions/036-channel-0-pre-negotiated-call.md) | Channel 0 Pre-Negotiated | Channel 0 = alk/call |
 | [042](decisions/042-hub-relay-translate-not-forward.md) | Hub Relay | Translate channel 0, byte-forward data channels |
 | [041](decisions/041-per-identity-channel-cap.md) | Per-Identity Channel Cap | 256 per PeerId, enforced via ChannelLifecyclePolicy in channels-call (amended by ADR-047 §7 — opener ledger, every teardown path) |
 | [035](decisions/035-channels-pure-channel-multiplexing.md) | Pure Channel Multiplexing | No stream_types; handler owns sub-mux |