docs: record the streaming-rebuild fix, its numbers, and the new scripts

RUST.md's P0 box gets the fix, the before/after streaming-phase numbers
(with their caveats), the build-apk.sh/run-bench.sh scripts, and what the
dropout-fix pass's three remaining verifications are blocked on (the
sandbox ai-server currently fails to build, unrelated to this change).
IRIS.md gets the List::replace_back/clear and TranscriptScreen::apply
API entries. AGENTS.md's rigs section gets one sentence on each script.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

AGENTS.md

@@ -261,6 +261,13 @@ Each exists because something was invisible without it.
   framework, from `atrace` text output with no trace processor needed. It is
   how the cost of a layout node per link was attributed to the framework
   rather than guessed at.
+- **`iris/android-app/build-apk.sh [debug|release] [--abi ...] [--features
+  ...]`** builds iris-android-app's cdylib (`cargo ndk`) and its APK
+  (Gradle) in one step and verifies the result (`aapt2`/`apksigner`), and
+  **`iris/android-app/run-bench.sh [--apk PATH]`** installs it on this
+  checkout's own emulator, taps "Run benchmark" by label, and prints the
+  report -- written so the P0 build/install/tap/read-report cycle stops
+  being retyped by hand each time (docs/RUST.md's P0 box).
 
 ### Driving the UI