docs: add P-* policy sections to policy doc

diff --git a/docs/policy.md b/docs/policy.md
index fd8968d7..8ee25cf2 100644
--- a/docs/policy.md
+++ b/docs/policy.md
@@ -1,4 +1,4 @@
-# Coding policy for the rust-bitcoin repository
+# Coding Policy for `rust-bitcoin`
 
 We have various `rust-bitcoin` specific coding styles and conventions that are
 grouped here loosely under the term 'policy'. These are things we try to adhere
@@ -6,6 +6,30 @@ to but that you should not need to worry too much about if you are a new
 contributor. Think of this as a place to collect group knowledge that exists in
 the various PRs over the last few years.
 
+## Table of Contents
+
+- [Import statements](#import-statements)
+- [Re-exports](#re-exports)
+  - [pub extern crates](#pub-extern-crates)
+  - [Special treatment of `bitcoin`, `primitives`, `units`](#special-treatment-of-bitcoin-primitives-units)
+  - [Usage of re-exports](#usage-of-re-exports)
+- [Consistent Exports (P-CONSISTENT-EXPORTS)](#consistent-exports-p-consistent-exports)
+- [Return `Self`](#return-self)
+- [Errors](#errors)
+  - [`From<Infallible>` (P-ERROR-INFALLIBLE)](#frominfallible-p-error-infallible)
+- [`expect` messages](#expect-messages)
+- [Rustdocs](#rustdocs)
+  - [Links](#links)
+  - [Examples](#examples)
+- [Derives](#derives)
+- [Attributes](#attributes)
+- [BIP References](#bip-references)
+  - [Exceptions](#exceptions)
+- [Arbitrary Implementations (P-ARBITRARY)](#arbitrary-implementations-p-arbitrary)
+- [Decoder Implementations (P-DECODERS)](#decoder-implementations-p-decoders)
+- [Default Values (P-DEFAULT-CHANGE)](#default-values-p-default-change)
+- [Licensing](#licensing)
+
 ## Import statements
 
 We use the following style for import statements, see
@@ -124,6 +148,10 @@ policy is to use types from the highest crate available i.e `use crate::Foo` not
 
 This is enforced by CI.
 
+## Consistent Exports (P-CONSISTENT-EXPORTS)
+
+Root package exports and module exports should remain consistent in stable crates. Once a type, function, or module is publicly exported, removing or changing its visibility in a later version is a breaking change. Carefully consider what should be part of the public API.
+
 ## Return `Self`
 
 Use `Self` as the return type instead of naming the type. When constructing the return value use
@@ -180,9 +208,9 @@ More specifically an error should
 - implement Display using `write_err!()` macro if a variant contains an inner error source.
 - have `Error` suffix on error types (structs and enums).
 - not have `Error` suffix on enum variants.
-- call `internals::impl_from_infallible!`.
 - implement `std::error::Error` if they are public (feature gated on "std").
 - have messages in lower case, except for proper nouns and variable names.
+- implement `From<Infallible>` (more on that below).
 
 ```rust
 /// Documentation for the `Error` type.
@@ -195,13 +223,20 @@ pub enum Error {
     B,
 }
 
-internals::impl_from_infallible!(Error);
-
+impl From<Infallible> for Error {
+    fn from(never: Infallible) -> Self { match never {} }
+}
 ```
 
 All errors that live in an `error` module (eg, `foo/error.rs`) and appear in a public function in
 `foo` module should be available from `foo` i.e., should be re-exported from `foo/mod.rs`.
 
+### `From<Infallible>` (P-ERROR-INFALLIBLE)
+
+All public error types should implement `From<Infallible>` to allow callers to seamlessly convert an operation that can never fail into one that is structurally designed to handle errors.
+
+[`Infallible`](https://doc.rust-lang.org/std/convert/enum.Infallible.html) is a "temporary" (years long) type system hack which should hopefully be replaced in the future by [a rust language feature](https://github.com/rust-lang/rfcs/blob/master/text/1216-bang-type.md). Implementing `Infallible` on rust-bitcoin errors allows callers to take advantage now and avoid orphan rule issues.
+
 ## `expect` messages
 
 With respect to `expect` messages, they should follow the
@@ -377,6 +412,21 @@ Module names, function names, variable names, and file names must keep their exi
 - Module names: `bip32`, `bip152` (keep lowercase)
 - Function names: `bip32_derivation`, `bip_341_tests` (keep existing format)
 
+## Arbitrary Implementations (P-ARBITRARY)
+
+Public types should implement the `Arbitrary` trait when a package has an `arbitrary` feature. This ensures helpful fuzz types for users to fuzz their own types built on the primitives exported by rust-bitcoin.
+
+## Decoder Implementations (P-DECODERS)
+
+Public decoder types defined with `bitcoin-consensus-encoding` follow standard conventions to ensure consistent API design for encoding/decoding infrastructure across the library.
+
+1. **`Default`** - Decoders should have a default constructor.
+2. **`new()` method** - Decoders should provide an explicit `new()` constructor method.
+
+## Default Values (P-DEFAULT-CHANGE)
+
+Default values should not change between versions, as this is a breaking change.
+
 ## Licensing
 
 We use SPDX license tags, all files should start with