init: /protocol replaces the ServiceId registry

A protocol is reached by name now, not by a compile-time integer. Init is
PID 1 and already knows which binary it started, so init serves /protocol
as a vfs backend: bind claims a contract with the provider's endpoint
attached, open answers with that endpoint as the reply's capability, and
readdir lists what is bound with the task and binary behind it. The kernel
reserves the prefix — nothing may mount over it, under it, or unmount it —
and ServiceId, ipc_register and ipc_lookup are gone, their syscall numbers
left vacant.

A bind is authorized by who the caller *is*: the kernel-stamped binary
together with the supervising task's identity, matched against
/system/configuration/protocol.csv. Identity, not spelling — spawn is
ungated, so an attacker can run any bundled binary, and a name-only rule
would have let it launder grants through an init of its own making. A name
a live process holds is refused to everyone else; a dead one's is released.

Three review rounds against a hostile ring-3 process found what 108 green
tests could not, because the suite contains no attacker. Publishing init's
supervision endpoint as the registry put PID 1's mailbox in every process's
hands, where two forged bytes reached the shutdown path: privileged traffic
is now believed only from the task that holds the contract it speaks for.
A capability arriving on a request outlived every path that ignored it,
one handle per call until the table was full — in init, and in the harness
ten services share — so the arriving capability is owned by the turn and
released unless a handler says otherwise. And the kernel let anyone holding
an endpoint handle aim signals, timers, exit notices and interrupts at it:
binding now requires having created it.

Suite 108/108. The new protocol-registry case asserts eleven properties,
each one an attack that must fail.

docs/security-track-plan.md

@@ -36,7 +36,7 @@ the logging/USB-lifecycle track).
 - [x] **H1** — the `user-memory` module; nine stragglers converted; leaf U/S+W checks (plus physmap-coverage confirmation, so an `mmio_map`'d buffer cannot fault ring 0 — this also closes the same hazard on the IPC path; `fs_resolve`'s out-capacity bound made overflow-safe; suite 107/107)
 - [x] **merge** group 1 → main, push (f3bc23c, 2026-07-31)
 - [x] **P1** — envelope module + `Define`; vfs `NodeKind.protocol` + open-reply-capability; client `Channel` (mechanics only, nothing converted; suite unchanged at 107)
-- [ ] **P2** — registry in init; `/protocol` reserved; ServiceId flag-day (11 binds, 17 lookups)
+- [x] **P2** — registry in init; `/protocol` reserved; ServiceId flag-day (11 binds, 17 lookups; `protocol.csv` grants, chain-attested identity, dead-owner rebind; the kernel's endpoint-death sweep generalized off the retired registry; suite 108/108). Three adversarial review rounds closed six defects a green suite had missed: a forged power event could shut the machine down; the ping path leaked a capability per call, first in init and then in the shared harness; supervisor attestation by name was defeated by a laundering deputy; and the kernel let any handle-holder bind signals, timers, exits and IRQs to an endpoint it did not own.
 - [ ] **P3** — open grants: `protocol.csv` enforcement, denial test
 - [ ] **merge** group 2 → main, push
 - [ ] **P4a** — clean protocols rebased onto `Define` (vfs, block, display, scanout, input)
@@ -87,6 +87,22 @@ that implements it.
    `init` for init's own children, `kernel` for harness-spawned fixtures),
    not in extra init.csv columns — today every post-path init.csv field is
    argv, and overloading that is ambiguous. init parses both files.
+   *(P2 spelling: the supervisor column carries the binary exactly as the
+   kernel stamped it, so init's own children say `/system/services/init` and
+   the drivers say `/system/services/device-manager`; `kernel` stays a bare
+   word because a kernel task has no binary. A trailing `*` on any field
+   matches a subtree, which is how decision 4's `/test/` rule is expressed.)*
+   *(Clarification, 2026-08-01: the supervisor column names **the authorized
+   supervising task, matched by identity** — the binary is how the row spells
+   it, but init checks the task id. `kernel` is satisfied only by supervisor
+   id 0 (which only the kernel confers — user `system_spawn` always stamps the
+   caller); init's own path only by this init's task id; any other path only by
+   a task init spawned itself or one the kernel spawned. Matching the supervisor
+   by *name* alone is defeated by a laundering deputy — an attacker runs its own
+   instance of `/system/services/init`, has that spawn `/system/services/input`,
+   and both stamped names satisfy the row while the chain is entirely the
+   attacker's. Walking to the root of the chain does not fix it either, since
+   the laundered chain still roots at the real PID 1.)*
 4. **Test fixtures bind under `/protocol/test/...`**, granted to any
    binary whose path starts `/test/` — the subtree-scoping rule from the
    design doc, dogfooded. `shared_memory_test` (the borrowed-ServiceId
@@ -115,6 +131,10 @@ that implements it.
    process-test) either spawn init first or move to init.csv-driven
    scenario boots — resolved per-case in P2 with the suite as the
    arbiter.
+   *(P2 resolution: init gained a `registry` argv role — it mounts
+   `/protocol`, reads the grants, and starts no services — and each affected
+   case calls `spawnRegistry(rd)` before its own providers. Every case keeps
+   its own spawn set, so no scenario had to be re-shaped.)*
 10. **The capsule-staleness caveat is documented, not fixed.** On-volume
     edits to `/system/configuration/*.csv` do not reach the initrd copy
     the loader boots (capsule shadows tree). Same drift exists today with