docs(rust-link): protocol 2 — the read path, and phase 3 as built

The specification the other three repositories are held against, plus the phase
record.

`PROTOCOL.md` §8 is the new contract. Its centre is one field: every frame now
carries `type` — `event`, `snapshot`, `reply`, `control` — and the sidecar files
on that and nothing else. That is the dumb-forwarder property made structural
rather than intended: ten new event kinds are zero change in Rust-Link, and only
a version adding an indexed column touches it at all.

Also in §8: the fifteen-kind catalogue and what each frame carries; `wipeId`
derived by the plugin, which REVERSES §3.2's "deriving one is the website's job"
and says why; boards re-sent on connect and on a cadence; the aggregate rule (a
hook that can fire more than once a second per player is a counter, not an
event); the void rule that stops a read-path hook vetoing a death or a login; and
`GET /feed`, a cursor route separate from `/events` because one route with two
orderings serves the wrong one to every caller that forgets the parameter.

§8.5 is the part to read twice. The classification of a kind as public or staff
is NOT on the wire, deliberately: a boundary declared by the sender is one a
compromised or out-of-date game host can widen, so the module holds a
default-deny allowlist and this table is what its test holds it against.

§8.8 corrects a catalogue rather than a defect: PLAN.md §10 sources
`rust.login.denied` from `CanUserLogin`, and that hook fires on every attempt —
the only way to learn of a denial from it is to be the denier. A denial is the
absence of an approval, and protocol 2 emits both facts so phase 10 can pair them.

`PLAYER_WALK.md` is new, and it exists because half this catalogue cannot fire
without somebody holding a mouse. Ten steps, what each one should produce, and
what counts as a pass — written so the walk can be run without watching the
output live, and so the answer afterwards is readable as a transcript.

PLAN.md §16 is phase 3 as built: the four decisions, the two defects only a
server that BOOTED with the plugin could find (a wipe id that was null for every
real session, and a two-second main-thread stall on unload), what was proven and
how, and — stated plainly rather than implied — the three measurements still
queued on the org lead.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016wDDVXWMDz82WqE1i969r4

README.md

@@ -85,8 +85,9 @@ share a shape and nothing else, so neither document is a fallback for the other.
 
 | Doc | What it covers |
 |---|---|
-| [PROTOCOL.md](rust-link/PROTOCOL.md) | **Canonical** — the game link and the website API, the four declaration sites of the wire version, and what protocol 1 defines |
+| [PROTOCOL.md](rust-link/PROTOCOL.md) | **Canonical** — the game link and the website API, the four declaration sites of the wire version, and what each protocol version defines: 1 the transport, 2 the read path |
 | [INTEGRATION.md](rust-link/INTEGRATION.md) | Standing the bridge up by hand, and which of the three components is wrong when it does not work |
+| [PLAYER_WALK.md](rust-link/PLAYER_WALK.md) | The half of the read path a console cannot reach: ten minutes on a rig with a player, step by step, with what each hook should produce |
 
 ### `android/`
 | Doc | What it covers |