initial addition of essential crypto, encoders, workflows and LLM instructions

pkg/crypto/p256k/README.md

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+# p256k1
+
+This is a library that uses the `bitcoin-core` optimized secp256k1 elliptic
+curve signatures library for `nostr` schnorr signatures.
+
+If you need to build it without `libsecp256k1` C library, you must disable cgo:
+
+    export CGO_ENABLED='0'
+
+This enables the fallback `btcec` pure Go library to be used in its place. This
+CGO setting is not default for Go, so it must be set in order to disable this.
+
+The standard `libsecp256k1-0` and `libsecp256k1-dev` available through the
+ubuntu dpkg repositories do not include support for the BIP-340 schnorr
+signatures or the ECDH X-only shared secret generation algorithm, so you must
+follow the following instructions to get the benefits of using this library. It
+is 4x faster at signing and generating shared secrets so it is a must if your
+intention is to use it for high throughput systems like a network transport.
+
+The easy way to install it, if you have ubuntu/debian, is the script
+[../ubuntu_install_libsecp256k1.sh](../../../scripts/ubuntu_install_libsecp256k1.sh),
+it
+handles the dependencies and runs the build all in one step for you. Note that
+it
+
+For ubuntu, you need these:
+
+    sudo apt -y install build-essential autoconf libtool  
+
+For other linux distributions, the process is the same but the dependencies are
+likely different. The main thing is it requires make, gcc/++, autoconf and
+libtool to run. The most important thing to point out is that you must enable
+the schnorr signatures feature, and ECDH.
+
+The directory `p256k/secp256k1` needs to be initialized, built and installed,
+like so:
+
+```bash
+cd secp256k1
+git submodule init
+git submodule update
+```
+
+Then to build, you can refer to the [instructions](./secp256k1/README.md) or
+just use the default autotools:
+
+```bash
+./autogen.sh
+./configure --enable-module-schnorrsig --enable-module-ecdh --prefix=/usr
+make
+sudo make install
+```
+
+On WSL2 you may have to attend to various things to make this work, setting up
+your basic locale (uncomment one or more in `/etc/locale.gen`, and run
+`locale-gen`), installing the basic build tools (build-essential or base-devel)
+and of course git, curl, wget, libtool and
+autoconf.
+
+## ECDH
+
+TODO: Currently the use of the libsecp256k1 library for ECDH, used in nip-04 and
+nip-44 encryption is not enabled, because the default version uses the Y
+coordinate and this is incorrect for nostr. It will be enabled soon... for now
+it is done with the `btcec` fallback version. This is slower, however previous
+tests have shown that this ECDH library is fast enough to enable 8mb/s
+throughput per CPU thread when used to generate a distinct secret for TCP
+packets. The C library will likely raise this to 20mb/s or more.