Stop compiling the GPL crate GPUI drags in behind the framework

Lumbridge is Apache-2.0, and decision 0023 quietly made it link
GPL-3.0-or-later. `crates/gpui/Cargo.toml` at the pinned revision carries
`ztracing.workspace = true` -- unconditional, not optional, not behind a
feature -- and `ztracing` is GPL-3.0-or-later, as are the `zlog` and
`ztracing_macro` it pulls. `sum_tree` asks for it too. The path is the ordinary
Linux build, not an `--all-features` artefact and not a dev-dependency:

    lumbridge -> gpui_platform -> gpui_linux -> gpui -> ztracing -> zlog
                                                                -> ztracing_macro

`cargo deny check licenses` failed on it, exit 4.

This is the second thing decision 0023 got wrong by reading the manifests of the
crates it added instead of resolving the graph; the first was believing there
were two Zed Git sources when there are five. Both were found by a gate that had
never been run.

There was no feature to turn off, so the choice was to relax the licence policy,
drop the framework, or stop compiling the crate. `ztracing` is now redirected by
a `[patch]` table at `crates/lumbridge-ztracing-shim`, a first-party
zero-dependency no-op under Apache-2.0. `zlog` and `ztracing_macro` were
reachable only through it and leave the lockfile with it.

The shim is small because the usage is: nine `#[instrument(skip_all)]` sites
across `gpui/src/svg_renderer.rs`, `sum_tree/src/sum_tree.rs` and
`sum_tree/src/cursor.rs`, and nothing else. Upstream's own crate compiles to
almost exactly this whenever the `ztracing` cfg is off, which is every build
that is not a Tracy profiling build, so no shipping behaviour is lost. It is a
proc-macro crate deliberately: such a crate can export nothing but proc macros,
so an upstream revision that starts using `ztracing::Span` or
`ztracing::info_span!` fails to compile and names the shim, rather than
resolving to something plausible.

`scripts/workspace-guard.sh` gained a third gate asserting, against Cargo.lock
rather than the manifest, that no `ztracing`, `zlog` or `ztracing_macro`
resolves to a Zed source and that the patch table is still present. `cargo deny`
already checks this, and the duplication is the point: `scripts/ci.sh`
downgrades a missing cargo-deny to a warning unless `LUMBRIDGE_CI_STRICT=1`, and
that is how the licence closure went ungated once already. A `[patch]` is an
unusually quiet thing to lose -- delete the table and everything still compiles,
still passes, and is GPL again.

Removing the three GPL rejections exposed a fourth that had been sitting beside
them and was never reported separately: `libbz2-rs-sys` under `bzip2-1.0.6`,
reached through async-compression <- http_client <- gpui. It is BSD-style and
permissive with no copyleft, and is allowed in `deny.toml` with that reasoning
written down. `cargo deny check licenses sources` is exit 0 for the first time.

The Git-source allowances in `deny.toml` are all still needed; the patched
crate's own source was `zed.git`, which `gpui` still requires.

Decision 0025 records the whole of it.

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

Cargo.toml

@@ -12,6 +12,7 @@ members = [
     "crates/lumbridge-terminal",
     "crates/lumbridge-theme",
     "crates/lumbridge-ui-fixture",
+    "crates/lumbridge-ztracing-shim",
     "tools/theme-gen",
 ]
 exclude = ["spikes"]
@@ -30,3 +31,28 @@ unsafe_code = "forbid"
 [workspace.lints.clippy]
 all = "warn"
 pedantic = "warn"
+
+# GPUI's transitive GPL dependency, replaced by a first-party no-op.
+#
+# `gpui` at the pinned revision carries `ztracing.workspace = true` --
+# unconditional and not behind a feature -- and `ztracing` is GPL-3.0-or-later,
+# as are the `zlog` and `ztracing_macro` it drags with it. All three land in the
+# ordinary Linux build, not merely under `--all-features`, which makes them a
+# licence problem for an Apache-2.0 product rather than a lint to silence.
+# `cargo deny check licenses` failed on exactly this.
+#
+# The graph uses one symbol from the crate: an `#[instrument(skip_all)]`
+# attribute, at nine sites across `gpui` and `sum_tree`. So `ztracing` is
+# redirected at a workspace crate that provides that attribute and nothing else.
+# `zlog` and `ztracing_macro` were reachable only through `ztracing` and leave
+# the resolved graph with it.
+#
+# The URL is the one Cargo.lock records for the source being replaced --
+# `git+https://github.com/zed-industries/zed.git?rev=...` -- and it must stay
+# spelled that way, `.git` included, or the patch silently applies to nothing.
+# `scripts/workspace-guard.sh` asserts the result rather than the intent: that
+# no `ztracing`, `zlog` or `ztracing_macro` resolves to a Zed source.
+#
+# Read crates/lumbridge-ztracing-shim/src/lib.rs before bumping the revision.
+[patch."https://github.com/zed-industries/zed.git"]
+ztracing = { path = "crates/lumbridge-ztracing-shim" }