feat: add support for patching registry dependencies (#7469)

## Overview

Implements support for patching registry dependencies (from forc.pub)
using the `[patch]` table in `Forc.toml`. Previously, only Git
dependencies could be patched, which created a workflow gap when
packages like `std` migrated from Git to the registry.

## Motivation

When `std` and other core packages moved to forc.pub registry,
developers lost the ability to:
- Test local changes to standard library code
- Use unreleased features from development branches
- Debug issues with instrumented versions of dependencies

This PR restores that capability by extending the existing patch system
to support registry packages.

## Implementation

### Key Features

1. **Registry Patching**: Use `[patch.'forc.pub']` to override registry
dependencies
2. **Multiple Source Types**: Patch with local path or Git repository
3. **Namespace Support**: Built-in support for namespaced packages
(implementation-ready for future use)
4. **Priority System**: Namespace-specific patches override generic
patches

## Usage

### Basic Usage

```toml
[dependencies]
std = "0.70.1"

[patch.'forc.pub']
std = { path = "../sway/sway-lib-std" }
```

### Patch with Git Branch

```toml
[dependencies]
std = "0.70.1"

[patch.'forc.pub']
std = { git = "https://github.com/fuellabs/sway", branch = "my-feature" }
```

### Workspace-Level Patches

```toml
[workspace]
members = ["contract-a", "contract-b"]

[patch.'forc.pub']
std = { path = "../custom-std" }
```

## Documentation

Updated user documentation in:
- `docs/book/src/forc/manifest_reference.md` - Complete patch section
rewrite with examples
- `docs/book/src/forc/workspaces.md` - Added registry patching examples
- Inline code documentation with TOML syntax notes

## Breaking Changes

None. This is a purely additive change. All existing Git patches
continue to work exactly as before.

## Notes

- **TOML Syntax**: Quotes are required: `[patch.'forc.pub']` not
`[patch.forc.pub]`
- **Source Matching**: Registry patches only apply to registry
dependencies
- **Namespace Support**: Implementation includes namespace support

<!-- CURSOR_SUMMARY -->
---

> [!NOTE]
> Adds support to patch registry dependencies using `[patch.'forc.pub']`
(with namespaced overrides and fallback), keeps Git patching intact, and
updates docs with examples.
> 
> - **Core (forc-pkg)**:
> - Extend `Source::dep_patch` to handle registry sources: checks
`[patch.'forc.pub/<namespace>']` first, then `[patch.'forc.pub']`; Git
patching unchanged.
>   - Add `reg::REGISTRY_PATCH_KEY` constant (`"forc.pub"`).
> - **Tests**:
> - Add unit tests covering flat/domain namespaces, namespace priority
vs. generic fallback, Git patch compatibility, and no-op cases.
> - **Docs**:
> - Update `docs/book/src/forc/manifest_reference.md` with registry
patching examples, notes on quoting keys, and clarifications.
> - Update `docs/book/src/forc/workspaces.md` with Git and registry
patching examples for workspaces.
> 
> <sup>Written by [Cursor
Bugbot](https://cursor.com/dashboard?tab=bugbot) for commit
089422a. This will update automatically
on new commits. Configure
[here](https://cursor.com/dashboard?tab=bugbot).</sup>
<!-- /CURSOR_SUMMARY -->

Author: kayagokalp

docs/book/src/forc/manifest_reference.md

@@ -220,7 +220,11 @@ experimental-private-modules = false
 
 ## The `[patch]` Section
 
-The [patch] section of `Forc.toml` can be used to override dependencies with other copies. The example provided below patches `https://github.com/fuellabs/sway` with the `test` branch of the same repo.
+The `[patch]` section of `Forc.toml` can be used to override dependencies with other copies. This is useful for testing local changes, using unreleased features, or debugging dependencies.
+
+### Patching Git Dependencies
+
+The example provided below patches `https://github.com/fuellabs/sway` with the `test` branch of the same repo.
 
 ```toml
 [project]
@@ -260,7 +264,40 @@ foo = { git = "https://github.com/foo/foo", branch = "master" }
 foo = { git = "https://github.com/foo/foo", branch = "test" }
 ```
 
-Note that each key after the `[patch]` is a URL of the source that is being patched.
+### Patching Registry Dependencies
+
+You can also patch dependencies from the registry (forc.pub) in the same way. This is particularly useful for testing local changes to `std` or other registry packages.
+
+```toml
+[project]
+authors = ["user"]
+entry = "main.sw"
+license = "Apache-2.0"
+name = "my_contract"
+
+[dependencies]
+std = "0.70.1"
+
+[patch.'forc.pub']
+std = { path = "../sway/sway-lib-std" }
+```
+
+In the example above, even though `std` version `0.70.1` would normally be fetched from the registry, the local path version is used instead.
+
+You can also patch registry dependencies with a git repository:
+
+```toml
+[dependencies]
+std = "0.70.1"
+
+[patch.'forc.pub']
+std = { git = "https://github.com/fuellabs/sway", branch = "my-feature" }
+```
+
+### Important Notes
+
+* **Quotes are required**: Each key after `[patch]` must be in quotes (e.g., `[patch.'forc.pub']`) because they contain special characters. Without quotes, TOML will interpret dots as nested tables.
+* **Source matching**: Git patches match Git dependencies, and registry patches match registry dependencies.
 
 ## The `[contract-dependencies]` section
 

docs/book/src/forc/workspaces.md

@@ -32,19 +32,30 @@ The `[patch]` section can be used to override any dependency in the workspace de
 
 It is not allowed to declare patch table in member of a workspace if the workspace manifest file contains a patch table.
 
-Example:
+Example with Git dependency:
 
 ```toml
 [workspace]
 members = ["member1", "path/to/member2"]
 
-
 [patch.'https://github.com/fuellabs/sway']
 std = { git = "https://github.com/fuellabs/sway", branch = "test" }
 ```
 
 In the above example each occurrence of `std` as a dependency in the workspace will be changed with `std` from `test` branch of sway repo.
 
+Example with registry dependency:
+
+```toml
+[workspace]
+members = ["contract-a", "contract-b", "script"]
+
+[patch.'forc.pub']
+std = { path = "../custom-std" }
+```
+
+In this example, all workspace members will use the local custom version of `std` instead of the registry version.
+
 ## Some `forc` commands that support workspaces
 
 * `forc build` - Builds an entire workspace.