iris is the framework alone; the app is one crate in app-rust/

Iris: "the organization of the rust rewrite is a mess right now... there
shouldn't be anything related to the app inside of iris. Iris is supposed
to be the UI framework alone." And, on the crate count: "I'm confused why
the app only code needs more than one crate though."

Nine cargo workspaces become three, and the port's project code -- which
sat in five places, four of them inside the framework -- becomes one crate,
`ai-app`, in `app-rust/`:

  client-core                -> app-rust/src/client
  iris/transcript-ui         -> app-rust/src/ui
  iris/transcript-fixture    -> app-rust/src/ui/fixture.rs + tests/ + touch/
  iris/desktop-app           -> app-rust/src/desktop + src/bin_desktop.rs
  iris/android-app           -> app-rust/src/android + android-project/
  android-shell              -> app-rust/src/shell

iris/ keeps core, macro, the iris crate, tabs-ui and rig-input, and now
mentions no session, transcript, setup or server anywhere.

Only two of the old splits had a reason that survived reading. event-model
stays a crate at the repo root because server/ depends on it too, so a
crate is what makes the backend and the app agree by construction. The two
Android .so names looked like a hard constraint -- a package produces one
library artifact -- until P2 turned out to already plan merging those two
Android apps into one; both faces now come out of libai_app.so, picked
apart by features so `--no-default-features --features shell` keeps wgpu,
parley and iris out of the Compose app's APK. docs/RUST.md's "One app
crate" has the rest, including what each remaining feature is for.

DECISIONS.md and SUBAGENTS.md move into docs/ with everything else.

Verified: ./run-tests.sh and `cd iris && cargo test` green, clippy and fmt
clean in all five workspaces, `cargo ndk -t x86_64` links libai_app.so,
build-apk.sh produces an APK that installs and launches on this checkout's
emulator (Gl ... virgl, as expected), and the phone-sized headless
screenshot renders the transcript unchanged.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

server/src/routes.rs

@@ -30,7 +30,7 @@
 //!                                     ?limit=N, ?coalesce=true to count rows not deltas,
 //!                                     ?after=N to floor it at what the caller already holds
 //! GET    /sessions/{id}/subagents     [{id, title, status, created, lastActivity}], oldest
-//!                                     first -- see SUBAGENTS.md
+//!                                     first -- see docs/SUBAGENTS.md
 //! GET    /sessions/{id}/subagents/{sub}/transcript  exactly the transcript route above,
 //!                                     against that subagent's own transcript
 //! GET    /sessions/{id}/subagents/{sub}/events?after=N  exactly the events route above,
@@ -1779,7 +1779,7 @@ async fn transcript(
 }
 
 /// Exactly [`transcript`]'s route and answer, against one subagent's own
-/// transcript instead of its session's -- see `SUBAGENTS.md`'s wire shape.
+/// transcript instead of its session's -- see `docs/SUBAGENTS.md`'s wire shape.
 async fn subagent_transcript(
     State(manager): State<Arc<SessionManager>>,
     UrlPath((id, sub)): UrlPath<(String, String)>,
@@ -1846,7 +1846,7 @@ async fn events(
 }
 
 /// Exactly [`events`]'s route and answer, against one subagent's own stream
-/// instead of its session's -- see `SUBAGENTS.md`'s wire shape.
+/// instead of its session's -- see `docs/SUBAGENTS.md`'s wire shape.
 async fn subagent_events(
     State(manager): State<Arc<SessionManager>>,
     UrlPath((id, sub)): UrlPath<(String, String)>,
@@ -1884,7 +1884,7 @@ fn sse_stream(
 
 /// `GET /sessions/{id}/subagents`: every subagent this session has started,
 /// oldest first, with a status read from its own transcript -- see
-/// `SUBAGENTS.md`'s wire shape. A subagent whose last status is `Running` is
+/// `docs/SUBAGENTS.md`'s wire shape. A subagent whose last status is `Running` is
 /// reported `Unknown` instead when the session itself is not running: its
 /// process was the session's, and a session with none has nothing left to
 /// ask.
@@ -1895,7 +1895,7 @@ async fn list_subagents(
     let session = lookup(&manager, &id)?;
     // Anything but `Exited` or `Unknown` has a process behind it, which is
     // what decides whether a subagent still reading `Running` from its own
-    // transcript can be believed -- see `SUBAGENTS.md`'s wire shape.
+    // transcript can be believed -- see `docs/SUBAGENTS.md`'s wire shape.
     let running = !matches!(
         session.status(),
         crate::session::driver::SessionStatus::Exited