docs: show pre-releases in the release badge, list the new gates

Every release is now published as a pre-release until it has been flashed to a
real calculator, and shields.io's github/v/release excludes pre-releases by
default -- the badge read "no releases or repo not found". Add
include_prereleases.

docs/index.html needs no change: /releases/latest redirects to the releases list
while no stable release exists, and points straight at one after promotion.

Also surface verify-install / check-budgets / sim-test in the README, and say why
a green `make` does not mean the app is installable.

Author: 1e1

README.md

@@ -4,7 +4,7 @@
 
 # RPN for NumWorks
 
-[![GitHub release](https://img.shields.io/github/v/release/1e1/numworks-RPN?style=flat-square)](https://github.com/1e1/numworks-RPN/releases)
+[![GitHub release](https://img.shields.io/github/v/release/1e1/numworks-RPN?include_prereleases&style=flat-square)](https://github.com/1e1/numworks-RPN/releases)
 [![GitHub commit activity](https://img.shields.io/github/commit-activity/m/1e1/numworks-RPN?style=flat-square&color=brightgreen)](https://github.com/1e1/numworks-RPN/commits/main)
 [![License](https://img.shields.io/github/license/1e1/numworks-RPN?style=flat-square)](https://github.com/1e1/numworks-RPN/blob/main/LICENSE)
 
@@ -105,15 +105,23 @@ Lower-frequency operations, navigated with `↑`/`↓` and `OK`, closed with
 Requires `arm-none-eabi-gcc` and Node.js (for [`nwlink`](https://www.npmjs.com/package/nwlink)).
 
 ```shell
-make            # build output/rpn.nwa
-make install    # build and upload to a plugged-in calculator
-make test       # build and run the host-side engine unit tests
+make                # build output/rpn.nwa
+make install        # build and upload to a plugged-in calculator
+make test           # host-side engine unit tests
+make verify-install # perform the install-time link, no calculator needed
+make check-budgets  # assert the RAM and 32 KiB-stack budgets
+make sim-test       # replay tests/sim in the Epsilon simulator (Docker)
 ```
 
 The numeric core (`src/value`, `src/stack`, `src/rpn`, `src/input_field`) is pure
 C++ with no calculator dependency, so `make test` compiles and runs it on your
 host machine.
 
+`make` only produces a *relocatable* object, so it cannot fail on undefined
+symbols — the link that decides whether a calculator can install the app happens
+later, and `verify-install` is what rehearses it. See
+[CONTRIBUTING.md](CONTRIBUTING.md#verifying-a-change) for which check catches what.
+
 ## Try it in a web simulator (Docker)
 
 Run the app in a browser via the Epsilon web simulator — only Docker is needed