Make the gate structural, and correct what it tells an agent

Three gates in this repository were decorative, and each was discovered by
being wrong rather than by failing.

A crate directory in neither members nor exclude is silently not built, which
is how lumbridge-devices shipped 1,127 lines that had never compiled.
scripts/workspace-guard.sh refuses that state, and asserts the gpui source
and version out of Cargo.lock rather than the manifest, because a manifest
states an intent while the lockfile states what would actually be compiled --
and a caret requirement accepts a version nobody reviewed. It needs no
compiler, so it runs first and in the headless job, which unlike the UI job
is not continue-on-error and can therefore actually fail a push.

deny.toml's source policy had never been executed: ci.sh ran `check
licenses` alone, and `check sources` failed immediately on the rev-pinned
buzz-sdk. The permitted Git sources are now named one by one and the check
runs, so a fourth is a decision rather than an accident.

cargo-deny and cargo-nextest being absent was a warning that let a run report
green having skipped the licence gate DISTRIBUTION.md depends on. Under
LUMBRIDGE_CI_STRICT=1 a missing tool now fails; locally it stays a warning so
a contributor is not blocked.

skills/lumbridge-development/SKILL.md told every agent that GPUI and Floem
live in spikes/ and that no framework may be selected until both pass the
hard gates. Decision 0017 settled that a month ago in the opposite direction.
The entry point an agent is meant to read was the least accurate document in
the repository.

Decision 0023 records where the GPUI dependency actually goes. Published gpui
has not been released since 2025-10-22, Zed's main still declares 0.2.2 with
no bump pending, the platform backends moved to crates that inherit
publish = false, gpui's own x11 and wayland features are now empty markers,
and 0.2.2 has no accesskit dependency at all -- so "published now, migrate
later" was never available. The adapter 0017 promised was never written and
the call sites grew from few to 147 against 20 identities, so the adapter is
written first, on 0.2.2, before the dependency moves.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01SPYebLiN2w4TqnHUYGdECq

AGENTS.md

@@ -43,14 +43,44 @@ workspace's `Research/` directory. They are references, not vendored code.
 - No telemetry is enabled by default. Any future telemetry must be documented,
   opt-in, redacted, and independently disableable.
 
+## Dependencies that are not an agent's decision
+
+The native UI framework is settled and its dependency is pinned by a decision
+record. Do not change the `gpui` (or `gpui_platform`) source, revision, or
+version; do not edit `rust-toolchain.toml` or the workspace `rust-version`; do
+not run `cargo update` or relax `deny.toml` to make a build succeed. A headless
+test asserts the pinned source and revision on every push, so a silent bump
+fails CI rather than landing.
+
+Changing any of them is a new decision record with a probe run at the new
+revision, not a commit. If a UI build fails, the failure is the finding: report
+it rather than routing around it.
+
+## Every crate is a workspace member
+
+A crate directory in neither `workspace.members` nor `workspace.exclude`
+inherits no lints, is never built, and its tests never run -- silently. This has
+happened twice here, and both times the code looked finished and did not
+compile. Add a crate to `members` in the same change that creates it, and never
+move code into an excluded directory to make a build pass. CI fails on a crate
+that is in neither list.
+
 ## Verification
 
 Before committing Rust changes, run:
 
 ```bash
+export PATH="$HOME/.cargo/bin:$PATH"   # a non-interactive shell has no cargo
 ./scripts/ci.sh
 ```
 
+`cargo` is on `PATH` only via an interactive shell profile, so an agent, an
+`ssh` command, or a hook gets `cargo: command not found` without that export.
+Never conclude a gate passed from an exit code obtained through a pipe -- a
+pipeline reports its last command's status, which has hidden a failing gate
+here already. `--headless` deliberately excludes `apps/lumbridge`, so a headless
+pass is not a product pass.
+
 Keep `bacon` running during development. Tests must use synthetic fixtures; real
 agent transcripts, subscription state, private source, and credentials are never
 test data.