docs: Update AGENTS.md to mandate 'yes | ./cargo.sh' (#2799)

* docs: Update AGENTS.md to mandate 'yes | ./cargo.sh'

The `./cargo.sh` wrapper (via `cargo-zerocopy`) interactively prompts
the user to install missing toolchains or components (e.g., `rust-src`).
This interactivity causes agents to hang or fail (e.g., panic on
unexpected EOF).

This change updates `AGENTS.md` to strictly require the usage of
`yes | ./cargo.sh` for all operations, ensuring that toolchain
installations are auto-confirmed in non-interactive environments.
All code examples and the syntax definition have been updated to
reflect this requirement.

* docs: Update AGENTS.md to mandate 'yes | ./cargo.sh' and reference fmt script

Updates `AGENTS.md` to:
1. Strictly require the usage of `yes | ./cargo.sh` for all operations to bypass interactive toolchain installation prompts.
2. Instruct agents to read `ci/check_fmt.sh` to determine how to format code.

All code examples and the syntax definition have been updated to reflect the `yes |` requirement.

---------

Co-authored-by: google-labs-jules[bot] <161369871+google-labs-jules[bot]@users.noreply.github.com>

Author: google-labs-jules[bot]

AGENTS.md

@@ -4,10 +4,10 @@ This repository uses a wrapper script around Cargo to ensure consistent toolchai
 
 ## Build and Test
 
-**IMPORTANT:** You must **NEVER** run `cargo` directly. Instead, you must **ALWAYS** use the `./cargo.sh` wrapper script for all `cargo` sub-commands (e.g., `check`, `test`, `build`).
+**IMPORTANT:** You must **NEVER** run `cargo` directly. Instead, you must **ALWAYS** use `yes | ./cargo.sh` for all `cargo` sub-commands (e.g., `check`, `test`, `build`). Using `yes |` is required to bypass interactive prompts for toolchain installation.
 
 ### Syntax
-`./cargo.sh +<toolchain> <command> [args]`
+`yes | ./cargo.sh +<toolchain> <command> [args]`
 
 ### Toolchains
 The `<toolchain>` argument is mandatory and can be one of the following:
@@ -23,23 +23,23 @@ The `<toolchain>` argument is mandatory and can be one of the following:
 Clippy should **always** be run on the `nightly` toolchain.
 
 ```bash
-./cargo.sh +nightly clippy
-./cargo.sh +nightly clippy --tests
+yes | ./cargo.sh +nightly clippy
+yes | ./cargo.sh +nightly clippy --tests
 ```
 
 ### Examples
 
 ```bash
 # Check the code using the nightly toolchain
 # DO NOT RUN: cargo check
-./cargo.sh +nightly check
+yes | ./cargo.sh +nightly check
 
 # Run tests on all supported toolchains
 # DO NOT RUN: cargo test
-./cargo.sh +all test
+yes | ./cargo.sh +all test
 
 # Run a specific test on stable
-./cargo.sh +stable test -- test_name
+yes | ./cargo.sh +stable test -- test_name
 ```
 
 ## Workflow
@@ -76,6 +76,10 @@ When a PR makes progress on, but does not close, an issue, the PR description an
 
 ## Code Style
 
+### Formatting
+
+To determine how to format code, read the formatting checker script in `ci/check_fmt.sh`.
+
 ### Comments
 
 All comments (including `//`, `///`, and `//!`) should be wrapped at 80 columns.