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

AGENTS.md

@@ -50,7 +50,7 @@ This is the call + channels RPC crate — the unification of
 `alknet-call` (structured JSON RPC: operations, streaming subscriptions,
 service discovery) and `alknet-channels` (multiplexing proxy: N logical
 channels over one transport stream, channel 0 pre-negotiated as
-`alknet/call`). The conventions below apply to all work in `src/` and
+ `alk/call`). The conventions below apply to all work in `src/` and
 `tests/`. They mirror `.opencode/agents/implementation-specialist.md`
 §Project Conventions and are repeated here so they apply to every
 session, not just spawned implementation agents.
@@ -205,8 +205,9 @@ If feature flags are added, also run `cargo test --all-features` and
   alknet mono-repo (`/workspace/@alkdev/alknet`). The source
   architecture docs were ported from
   `/workspace/@alkdev/alknet/docs/architecture/` and renumbered as
-  alkcall ADRs (001..047). The ALPN strings (`alknet/call`,
-  `alknet/channels`) are wire-stable and unchanged.
+  alkcall ADRs (001..047). The ALPN strings (`alk/call`,
+  `alk/channels`) are wire-stable going forward (renamed from
+  `alknet/` to `alk/` in v0.1.1, before the first published consumer).
 - Key ADRs that inform this crate's design:
 
   **Call protocol:**
@@ -240,7 +241,7 @@ If feature flags are added, also run `cargo test --all-features` and
   - ADR-034 — channels wire format (8-byte chunk header; one-way door)
   - ADR-035 — channels pure channel multiplexing (no `stream_type`,
     `BiStream`-only, handler owns sub-stream multiplexing)
-  - ADR-036 — channel 0 pre-negotiated as `alknet/call`
+  - ADR-036 — channel 0 pre-negotiated as `alk/call`
   - ADR-037 — channel lifecycle operations (`channel/open`/`close`/
     `control`/`resources/subscribe` on channel 0's call registry)
   - ADR-039 — `ChannelsAdapter` and `ChannelManager` (substrate-agnostic
@@ -260,7 +261,7 @@ If feature flags are added, also run `cargo test --all-features` and
   - ADR-002 — `ProtocolHandler` trait
   - ADR-003 — auth as shared core (`IdentityProvider` in core,
     handlers extract credentials)
-  - ADR-004 — ALPN string convention (`alknet/` prefix, one ALPN per
+  - ADR-004 — ALPN string convention (`alk/` prefix, one ALPN per
     connection)
   - ADR-005 — `BiStream` type definition (handlers receive
     `Connection`, not `BiStream`)