Plan M4b: approvals over Mattermost in 15 tasks

Skeletons for new files only; existing files change by exact edits, so no task overwrites an
earlier one's work. Each task's tests were run against a reference built in order from master,
with the gate at each step and mutations checked; each skeleton compiles and fails its tests, and
every todo!() comment was read beside its signature. The reference is kept off this machine.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

docs/plans/M4b/files/crates/proto/tests/fixtures/wire/gateway_outcome_denied.json

@@ -0,0 +1 @@
+{"v":1,"id":2,"final":true,"msg":{"kind":"approval_outcome","body":{"outcome":{"outcome":"denied","reason":"no_grant"}}}}

docs/plans/M4b/files/crates/proto/tests/fixtures/wire/gateway_outcome_gone.json

@@ -0,0 +1 @@
+{"v":1,"id":2,"final":true,"msg":{"kind":"approval_outcome","body":{"outcome":{"outcome":"gone"}}}}

docs/plans/M4b/files/crates/proto/tests/fixtures/wire/gateway_outcome_refused.json

@@ -0,0 +1 @@
+{"v":1,"id":2,"final":true,"msg":{"kind":"approval_outcome","body":{"outcome":{"outcome":"refused"}}}}

docs/plans/M4b/files/crates/proto/tests/fixtures/wire/gateway_outcome_runs.json

@@ -0,0 +1 @@
+{"v":1,"id":2,"final":true,"msg":{"kind":"approval_outcome","body":{"outcome":{"outcome":"runs"}}}}

docs/plans/M4b/files/crates/proto/tests/fixtures/wire/gateway_posted.json

@@ -0,0 +1 @@
+{"v":1,"id":1,"final":false,"msg":{"kind":"approval_posted","body":{"posts":["p0000000000000000000000001","p0000000000000000000000002"]}}}

docs/plans/M4b/files/crates/proto/tests/fixtures/wire/gateway_reply_approved.json

@@ -0,0 +1 @@
+{"v":1,"id":1,"final":true,"msg":{"kind":"approval_reply","body":{"approval":41,"approved":true,"by":"k0000000000000000000000000","post":"c0000000000000000000000001","reason":null}}}

docs/plans/M4b/files/crates/proto/tests/fixtures/wire/gateway_reply_refused.json

@@ -0,0 +1 @@
+{"v":1,"id":1,"final":true,"msg":{"kind":"approval_reply","body":{"approval":41,"approved":false,"by":"k0000000000000000000000000","post":"c0000000000000000000000001","reason":"not on a Friday"}}}

docs/plans/M4b/files/crates/proto/tests/fixtures/wire/gateway_request.json

@@ -0,0 +1 @@
+{"v":1,"id":1,"final":true,"msg":{"kind":"approval_request","body":{"approval":{"approval":41,"session":"mm-r0000000000000000000000001","call":3,"tool":"shell","arguments":"{\"command\":\"ls -la /srv\"}","grant":"shell-srv","taint":"private","created":"2026-09-24T08:05:00.000Z","expires":"2026-09-24T08:20:00.000Z"}}}}