docs: reflect arm-port carve-out; master is x86-only, aarch64 on branch

Mainline now carries roadmap #1-#5; the aarch64 context-switch port is a single untested commit on the arm-port branch. Update the task.md resume block and the README build section accordingly.

README.md

@@ -67,8 +67,10 @@ benches/
 ## Building and running
 
 Standard Cargo. Requires Rust 1.95 or newer (the `#[naked]` attribute went stable
-in 1.88; we use a few unrelated post-1.88 features). x86-64 Linux only —
+in 1.88; we use a few unrelated post-1.88 features). `master` is x86-64 Linux
-ARM64 and macOS are on the deferred list because of the assembly shim and the
+only. An experimental, **untested** aarch64 context-switch backend lives on the
+`arm-port` branch (extracted into a `target_arch`-gated `src/arch/`); it has not
+been validated on hardware yet. macOS remains on the deferred list because of the
 epoll dependency.
 
 ```sh

task.md

@@ -5,17 +5,19 @@ before starting; the gotchas section is hard-won and will save you a faceplant.
 
 ## Resume the environment
 
-- Repo: `/home/claude/work/smarm`, branch `arm-port`, currently 8 commits past
+- Repo: `smarm`. Two branches (the old single `arm-port` stack was split):
-  `master`:
+  - `master` — the mainline, and HEAD. Carries roadmap #1–#5: cooperative
-  - `a8fec02` aarch64 context-switch port
+    cancellation, supervisor strategies (one_for_one/all, rest_for_one) + the
-  - `183fd05` monitors (`monitor()` → `Receiver<Down>`)
+    orphaned-timer shutdown fix, links/trap_exit, selective receive, gen_server,
-  - `f617266` one-for-one supervisor (restart policies + intensity cap)
+    and demonitor/`MonitorId`. Tagged `v0.4.0`. x86-64 Linux only.
-  - `a8ddb4a` cooperative cancellation (roadmap #1 — done)
+  - `arm-port` — `master` plus a single commit: `feat(arch): aarch64 context
-  - `e80334b` fix: orphaned timers no longer block runtime shutdown
+    switch + cycle counter`. Extracts the x86-64 context-switch / stack-init /
-  - `351dc9c` one_for_all / rest_for_one + ordered shutdown (roadmap #2 — done)
+    cycle-counter out of `context.rs` into a `target_arch`-gated `src/arch/`
-  - `31133a6` docs(roadmap): mark #1 and #2 done
+    (x86_64 + aarch64 backends) and adds an AAPCS64 backend. ⚠️ UNTESTED: never
-  - `6581484` links + trap_exit (roadmap #3 — done)
+    built or run on real ARM hardware. The x86-64 path is unchanged
-  - (+ a trailing docs commit marking #3 done and refreshing supervisor/README)
+    (`arch/x86_64.rs` is the old `context.rs` body verbatim), so the x86 suite
+    passing says nothing about the aarch64 backend. Build + test on-device
+    before trusting it.
 - Toolchain is installed but NOT on PATH in a fresh shell. First line of every
   session: `. "$HOME/.cargo/env"` (rustc/cargo 1.96).
 - Build `cargo build` · all tests `cargo test` · one suite `cargo test --test monitor`.
@@ -217,8 +219,11 @@ Shipped. What landed vs the plan:
   - Pure additive layer (no Slot/scheduler/spawn/finalize change) → no perf
     check run. Tests (`tests/gen_server.rs`): cast→call roundtrip, init/terminate
     ordering, both server-down paths.
-- Docs lag: README still says "x86-64 Linux only — ARM64 … deferred" and the
+- Docs: README now points at the experimental, untested aarch64 port on the
-  module table calls `context` x86-64-only; update for the aarch64 backend.
+  `arm-port` branch. The module table still calls `context` x86-64-only — true
+  for `master`, since the `src/arch/` split rides on `arm-port`. Fold the arch/
+  split and ARM64-supported wording into the README module table + build section
+  once `arm-port` is validated on hardware and merged.
 
 ## Gotchas / invariants (respect these)